chore: Update availability and other compilation issues after latest rebase.

Author: scottmarchant

Tests/DispatchAsyncTests/AsyncSemaphoreTests.swift

@@ -2,6 +2,7 @@ import Testing
 
 @testable import DispatchAsync
 
+@available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)
 @Test(.timeLimit(.minutes(1)))
 func asyncSemaphoreWaitSignal() async throws {
     let semaphore = AsyncSemaphore(value: 1)

Tests/DispatchAsyncTests/DispatchGroupTests.swift

@@ -20,10 +20,12 @@ import class Foundation.Thread
 import Testing
 
 private typealias DispatchGroup = DispatchAsync.DispatchGroup
+private typealias DispatchQueue = DispatchAsync.DispatchQueue
 
 @Suite("DispatchGroup Tests")
 struct DispatchGroupTests {
     @Test
+    @available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)
     func dispatchGroupOrderCleanliness() async throws {
         // Repeating this 1000 times to help rule out
         // edge cases that only show up some of the time
@@ -133,6 +135,7 @@ struct DispatchGroupTests {
     /// math-heavy blocks on a global queue, then waiting for them to finish with a
     /// timeout.  It also verifies that `notify` is invoked exactly once.
     @Test(.timeLimit(.minutes(1)))
+    @available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)
     func dispatchGroupStress() async throws {
         let iterations = 1000
         // We use a separate concurrent queue rather than the global queue to avoid interference issues

Tests/DispatchAsyncTests/DispatchPingPongTests.swift

@@ -1,6 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 PassiveLogic, Inc.
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+@_spi(DispatchAsync) import DispatchAsync
 import Testing
 
-@testable import DispatchAsync
+private typealias DispatchQueue = DispatchAsync.DispatchQueue
 
 /// Ping-Pong queue test  is adapted from the test
 /// [dispatch_pingpong.c in libdispatch](https://github.com/swiftlang/swift-corelibs-libdispatch/blob/main/tests/dispatch_pingpong.c).

Tests/DispatchAsyncTests/DispatchTimeIntervalTests.swift

@@ -1,6 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 PassiveLogic, Inc.
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+@_spi(DispatchAsync) import DispatchAsync
 import Testing
 
-@testable import DispatchAsync
+private typealias DispatchTimeInterval = DispatchAsync.DispatchTimeInterval
 
 @Test
 func dispatchTimeIntervalEquality() throws {

Tests/DispatchAsyncTests/DispatchTimeTests.swift

@@ -29,6 +29,7 @@ func testDispatchTimeContinousClockBasics() async throws {
     #expect(b < c)
 }
 
+@available(macOS 13, iOS 16, tvOS 16, watchOS 9, *)
 @Test
 func testUptimeNanosecondsEqualityForConsecutiveCalls() async throws {
     let original = DispatchTime.now()