[various] Update example apps to Swift

[stuartmorgan-g]

Converts the Objective-C iOS example apps for all non-iOS-plugin-implementation packages to Swift.

The process for this was (all using current stable, 3.32):

• Deleted example/ios.
• Ran flutter create --platforms=ios ..
• Reverted changes in ios/Runner/Assets.xcassets/AppIcon.appiconset (this doesn't really matter either way, I just decided not to thrash a bunch of icons, since there's no real reason to and it would have added a ton more files).
• Reverted changes outside of ios/, except for .gitignore which we may as well have a current version of.
• Added license blocks to template-created code files.
• Removed the RunnerTest target, its source file, and the Podfile adjustment to RunnerTest.
• Reverted bundle identifier changes in most cases, since it was often auto-detecting the old io.flutter.* org the examples were first created with.
• Re-added any important bits to Info.plist.
• Ran a build both with and without SwiftPM enabled, to ensure that all the Cocoapods and SwiftPM boilerplate is added to the projects to cut down on random diffs when people build later.

One-off changes:

• Added back Configuration.storkekit in in_app_purchase.
• Migrated the Google Maps API key code in AppDelegate.m to AppDelegate.swift

I did not convert the implementation packages in this PR because those will need to be handled more carefully, due to the presence of RunnerTest (and sometimes RunnerUITest) targets that need to be preserved.

Part of flutter/flutter#148586

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or I have commented below to indicate which version change exemption this PR falls under¹.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

Footnotes

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩² ↩³

[stuartmorgan-g]

CHANGELOG override: build details of example apps are not relevant to clients.

[stuartmorgan-g]

Version override: The false_secrets removal in extension_google_sign_in_as_googleapis_auth's pubspec.yaml flags for a version change, but that's not something that matters if we publish.

[stuartmorgan-g]

@jmagman / @vashworth Do you want me to wait for someone on the iOS team to review this, or should I just land it?