fix(test): remove placement timeout race

[ReubenBond]

Problem

GetOrPlaceActivationAsync_WhenLookupDoesNotComplete_TimesOut advances its fake clock to fire the placement timeout, then requires the resulting asynchronous cancellation propagation to complete within one second of wall-clock time. Under the loaded Windows BVT process, that continuation can be delayed long enough for the real-time delay to win even though the timeout has fired correctly.

Solution

Await the placement task directly using the xUnit cancellation token and assert its timeout outcome. This preserves a bounded test while removing the scheduler race between the placement continuation and an unrelated wall-clock delay.

Fixes #10852

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Copilot review overview

Review tier: Lite
Findings: None

What changed in this PR

Removes a timing-sensitive race in an Orleans runtime placement timeout unit test by switching from a Task.WhenAny(..., Task.Delay(...)) wall-clock gate to awaiting the placement task directly with xUnit’s cancellation token, aligning the test with how timeouts are driven via FakeTimeProvider.

Changes:

• Replaces Task.WhenAny(placementTask, Task.Delay(1s)) + Assert.Same with placementTask.WaitAsync(TestContext.Current.CancellationToken) inside Assert.ThrowsAsync<TimeoutException>.
• Keeps the existing assertions on the TimeoutException and its Polly.Timeout.TimeoutRejectedException inner exception.

File	Description
test/​Orleans.Core.Tests/​Runtime/​PlacementServiceTests.cs	Updates the flaky timeout test to avoid a wall-clock scheduling race while still keeping the await bounded by the test runner’s cancellation token.

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