**Motivation:**

Remove old benchmark infra which causes sendability warnings.

There's proper benchmark packages now and we should use them instead,
depend on: https://github.com/ordo-one/package-benchmark.git

**Modifications:**
Remove custom benchmark infra.
Adopt existing benchmark package -- this can also nicely track
allocations.

**Result:**

No sendability warnings; less deprecated benchmark infra

Author: ktoso

Benchmarks/.gitignore

@@ -0,0 +1 @@
+.build/

Benchmarks/.gitkeep

@@ -0,0 +1,87 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Distributed Tracing open source project
+//
+// Copyright (c) 2020-2023 Apple Inc. and the Swift Distributed Tracing project
+// authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Benchmark
+import Tracing 
+
+let benchmarks = {
+    let defaultMetrics: [BenchmarkMetric] = [
+        .mallocCountTotal,
+    ]
+
+    Benchmark(
+        "NoopTracing.startSpan/endSpan",
+        configuration: .init(
+            metrics: defaultMetrics,
+            timeUnits: .nanoseconds,
+            scalingFactor: .mega
+        )
+    ) { benchmark in
+        let span = startSpan("name")
+        defer { span.end() }
+    }
+
+    Benchmark(
+        "NoopTracing.attribute: set, span.attributes['http.status_code'] = 200",
+        configuration: .init(
+            metrics: defaultMetrics,
+            timeUnits: .nanoseconds,
+            scalingFactor: .mega
+        )
+    ) { benchmark in
+        let span = startSpan("name")
+        span.attributes["http.status_code"] = 200
+        defer { span.end() }
+    }
+
+    Benchmark(
+        "NoopTracing.attribute: set, span.attributes.http.status_code = 200",
+        configuration: .init(
+            metrics: defaultMetrics,
+            timeUnits: .nanoseconds,
+            scalingFactor: .mega
+        )
+    ) { benchmark in
+        let span = startSpan("name")
+        span.attributes.http.statusCode = 200
+        defer { span.end() }
+    }
+}
+
+@dynamicMemberLookup
+struct HTTPAttributes: SpanAttributeNamespace {
+    var attributes: SpanAttributes
+
+    init(attributes: SpanAttributes) {
+        self.attributes = attributes
+    }
+
+    struct NestedSpanAttributes: NestedSpanAttributesProtocol {
+        init() {}
+
+        var method: Key<String> { "http.method" }
+        var statusCode: Key<Int> { "http.status_code" }
+    }
+}
+
+extension SpanAttributes {
+    var http: HTTPAttributes {
+        get {
+            .init(attributes: self)
+        }
+        set {
+            self = newValue.attributes
+        }
+    }
+}

Benchmarks/Benchmarks/TracingBenchmarks/AtrributeDSLBenchmark.swift

@@ -0,0 +1,40 @@
+// swift-tools-version: 5.9
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftCertificates open source project
+//
+// Copyright (c) 2023 Apple Inc. and the SwiftCertificates project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftCertificates project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import PackageDescription
+
+let package = Package(
+    name: "benchmarks",
+    platforms: [
+        .macOS("14"),
+    ],
+    dependencies: [
+        .package(path: "../"),
+        .package(url: "https://github.com/ordo-one/package-benchmark.git", from: "1.22.0"),
+    ],
+    targets: [
+        .executableTarget(
+            name: "TracingBenchmarks",
+            dependencies: [
+                .product(name: "Benchmark", package: "package-benchmark"),
+                .product(name: "Tracing", package: "swift-distributed-tracing"),
+            ],
+            path: "Benchmarks/TracingBenchmarks",
+            plugins: [
+                .plugin(name: "BenchmarkPlugin", package: "package-benchmark")
+            ]
+        ),
+    ]
+)