Summary

• Xcode dedupes a real retry failure against the prior run's expected failure when both runs share a test identity. That hid genuine failures emitted on the final attempt for tests routed through ATR/EFD.
• XCTestCase.addAlias(of:named:) (new, in XCTestExtensions.swift) registers an instance method whose IMP and type encoding are copied from the original test method. Works for sync, throws, async, and methods with return values.
• DDXCTestRetryGroup.retry() now allocates each retry instance with an alias selector (testFoo$2, testFoo$3, ...). XCTest's invocation-derived -name makes Xcode treat each attempt as a separate test run.
• DDXCTestRetryGroup.perform(_:) uses the group's captured testId.test (original) for withActiveTest(named:), so the backend keeps a stable test name across retries.
• Bundles two unrelated drive-by cleanups: drop a stale try in SwiftTestingTrait.prepare(test:) (the call no longer throws) and format elapsed time in Log.measure with %.5f.

Test plan

• xcodebuild test -only-testing:DatadogSDKTestingTests/DDXCTestObserverTests -only-testing:DatadogSDKTestingTests/SwiftTestingTraitTests — green locally
• Run an integration test where ATR retries a failing XCTest method; confirm Xcode surfaces every retry's final failure (no dedup against earlier expected failures) and that the backend reports a single test with the original name across attempts
• Sanity-check an async/throws XCTest retry to confirm the aliased selector dispatches correctly

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