- combine `RegexReplace` into `PrintTestRunSummary` task
  - remove unused `WarnOnNoMatch` parameter; inline other parameters
  - capture test summary in `msbuild` logs
    - avoid `System.Console` use in the task
  - fail task if any tests fail
- collect `xunit` task exit codes in case of catastrophic problems (not test failures)
  - fail build if `PrintTestRunSummary` doesn't but errors occurred

also:
- do not test assemblies in parallel; reduce port contention issues
- avoid `CallTarget` task

nits:
- clean some trailing whitespace in C# sources
  - mostly files I expect to update soon
- reduce `NuGet.exe restore` verbosity; no longer debugging that
- add console summary when using build.cmd
- reduce duplication in `RestorePackages` target
  - only restore NetCore projects when `$(BuildPortable)` is `true`
  - restore src NetStandard project transitively through NetStandard.Test project
- pass more properties w/ `Restore` target invocation

- also bump Newtonsoft.Json.Bson to 1.0.2 in System.Net.Http.Formatting.NetStandard
- incorporates changes from 23 Dependabot PRs; they are now obsolete
  - Dependabot also left `@(Reference)` items alone in project files 😦
  - fixed what Dependabot didn't do i.e. corrected paths and assembly identities in those items

<details>
<summary>Release notes</summary>
<p><em>Sourced from <a href="https://github.com/JamesNK/Newtonsoft.Json/releases">Newtonsoft.Json's releases</a>.</em></p>
<blockquote>
<h2>13.0.1</h2>
<ul>
<li>New feature - Add JsonSelectSettings with configuration for a regex timeout</li>
<li>Change - Remove portable assemblies from NuGet package</li>
<li>Change - JsonReader and JsonSerializer MaxDepth defaults to 64</li>
<li>Fix - Fixed throwing missing member error on ignored fields</li>
<li>Fix - Fixed various nullable annotations</li>
<li>Fix - Fixed annotations not being copied when tokens are cloned</li>
<li>Fix - Fixed naming strategy not being used when deserializing dictionary enum keys</li>
<li>Fix - Fixed serializing nullable struct dictionaries</li>
<li>Fix - Fixed JsonWriter.WriteToken to allow null with string token</li>
<li>Fix - Fixed missing error when deserializing JToken with a contract type mismatch</li>
<li>Fix - Fixed JTokenWriter when writing comment to an object</li>
</ul>
<h2>12.0.3</h2>
<ul>
<li>New feature - Added support for nullable reference types</li>
<li>New feature - Added KebabCaseNamingStrategy</li>
<li>Change - Package now uses embedded package icon</li>
<li>Fix - Fixed bug when merging JToken with itself</li>
<li>Fix - Fixed performance of calling ICustomTypeDescriptor.GetProperties</li>
<li>Fix - Fixed serializing Enumerable.Empty and empty arrays on .NET Core 3.0</li>
<li>Fix - Fixed deserializing some collection types with constructor</li>
<li>Fix - Fixed deserializing IImmutableSet to ImmutableHashSet instead of ImmutableSortedSet</li>
<li>Fix - Fixed deserializing IImmutableDictionary to ImmutableDictionary instead of ImmutableSortedDictionary</li>
<li>Fix - Fixed deserializing into constructors with more than 256 parameters</li>
<li>Fix - Fixed hang when deserializing JTokenReader with preceding comment</li>
<li>Fix - Fixed JSONPath scanning with nested indexer</li>
<li>Fix - Fixed deserializing incomplete JSON object to JObject</li>
<li>Fix - Fixed using StringEnumConverter with naming strategy and specified values</li>
</ul>
<h2>12.0.2</h2>
<ul>
<li>New feature - Added MissingMemberHandling to JsonObjectAttribute and JsonObjectContract</li>
<li>New feature - Added constructor to JTokenReader to specify initial path</li>
<li>New feature - Added JsonProperty.IsRequiredSpecified</li>
<li>New feature - Added JsonContract.InternalConverter</li>
<li>Change - Moved embedded debug symbols in NuGet package to a symbol package on NuGet.org</li>
<li>Fix - Fixed deserializing nullable struct collections</li>
<li>Fix - Fixed memory link when serializing enums to named values</li>
<li>Fix - Fixed error when setting JsonLoadSettings.DuplicatePropertyNameHandling to Replace</li>
</ul>
<h2>12.0.1</h2>
<ul>
<li>New feature - Added NuGet package signing</li>
<li>New feature - Added Authenticode assembly signing</li>
<li>New feature - Added SourceLink support</li>
<li>New feature - Added constructors to StringEnumConverter for setting AllowIntegerValue</li>
<li>New feature - Added JsonNameTable and JsonTextReader.PropertyNameTable</li>
<li>New feature - Added line information to JsonSerializationException</li>
<li>New feature - Added JObject.Property overload with a StringComparison</li>
<li>New feature - Added JsonMergeSettings.PropertyNameComparison</li>
<li>New feature - Added support for multiple Date constructors with JavaScriptDateTimeConverter</li>
<li>New feature - Added support for strict equals and strict not equals in JSON Path queries</li>
</ul>
<!-- raw HTML omitted -->
</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/JamesNK/Newtonsoft.Json/commit/ae9fe44e1323e91bcbd185ca1a14099fba7c021f"><code>ae9fe44</code></a> Remove compiler package and update sourcelink (<a href="https://github-redirect.dependabot.com/JamesNK/Newtonsoft.Json/issues/2498">#2498</a>)</li>
<li><a href="https://github.com/JamesNK/Newtonsoft.Json/commit/8ef662189dd7fc890c8fcd832d3e283edb90ef31"><code>8ef6621</code></a> Remove prerelease for 13.0.1</li>
<li><a href="https://github.com/JamesNK/Newtonsoft.Json/commit/11331f50fd1c09dc1f44fe17ef26aba7c460b42c"><code>11331f5</code></a> Update SDK to 5.0.200 (<a href="https://github-redirect.dependabot.com/JamesNK/Newtonsoft.Json/issues/2495">#2495</a>)</li>
<li><a href="https://github.com/JamesNK/Newtonsoft.Json/commit/c7e8abc09de751785355e3f972150f8a72379b02"><code>c7e8abc</code></a> Update to 13.0.1-beta2</li>
<li><a href="https://github.com/JamesNK/Newtonsoft.Json/commit/1745d7c14ec7e4244a5ca1c7ddf5d955cf7d1f43"><code>1745d7c</code></a> Fix JTokenWriter when writing comment to an object (<a href="https://github-redirect.dependabot.com/JamesNK/Newtonsoft.Json/issues/2493">#2493</a>)</li>
<li><a href="https://github.com/JamesNK/Newtonsoft.Json/commit/583eb120152f8b6332df2fe3d4b9f4c947c944d0"><code>583eb12</code></a> Fix missing error when deserializing JToken with a contract type mismatch (<a href="https://github-redirect.dependabot.com/JamesNK/Newtonsoft.Json/issues/2">#2</a>...</li>
<li><a href="https://github.com/JamesNK/Newtonsoft.Json/commit/b6dc05be5a0f4808f06ec430f3bb59b24d3fbc3e"><code>b6dc05b</code></a> Change MaxDepth default to 64 (<a href="https://github-redirect.dependabot.com/JamesNK/Newtonsoft.Json/issues/2473">#2473</a>)</li>
<li><a href="https://github.com/JamesNK/Newtonsoft.Json/commit/15525f1c44e0d99ef8fdee73430853e22239181d"><code>15525f1</code></a> Fix JsonWriter.WriteToken to allow null with string token (<a href="https://github-redirect.dependabot.com/JamesNK/Newtonsoft.Json/issues/2472">#2472</a>)</li>
<li><a href="https://github.com/JamesNK/Newtonsoft.Json/commit/926d2f0f42292cfcdf07cdadeb501b73fd5b1d52"><code>926d2f0</code></a> Enable embed untracked sources (<a href="https://github-redirect.dependabot.com/JamesNK/Newtonsoft.Json/issues/2471">#2471</a>)</li>
<li><a href="https://github.com/JamesNK/Newtonsoft.Json/commit/0a56633b6cd4fccc860a8486260ee67636f3fe90"><code>0a56633</code></a> Fixes <a href="https://github-redirect.dependabot.com/JamesNK/Newtonsoft.Json/issues/2372">#2372</a> - variable typos (<a href="https://github-redirect.dependabot.com/JamesNK/Newtonsoft.Json/issues/2465">#2465</a>)</li>
<li>Additional commits viewable in <a href="https://github.com/JamesNK/Newtonsoft.Json/compare/6.0.4...13.0.1">compare view</a></li>
</ul>
</details>

- react to `BsonReader`, `BsonWriter` deprecation
- one of our `DateTime` tests now consistently hits `5` errors
- `s/True/true/` also consistent now in another test

- where possible, entirely remove app.config files
- w/ consistent Newtonsoft.Json versions, these special cases are mostly not needed
  - auto-generation of .config file handles the special case just fine in
  System.Net.Http.Formatting.NetStandard.Test.csproj and System.Web.Http.SignalR.Test.csproj