Split TimeoutTests into separate classes with single asset each

[Copilot]

TimeoutTests had 7 assets in a single GetAssetsToGenerate override, causing all assets to build during class initialization regardless of which tests run — blocking parallelism and wasting build time.

Changes

• TimeoutTests.cs — stripped to only the 5 CLI --timeout extension tests (asset: TimeoutTest)
• TimeoutWhenCanceledTests.cs — *_WhenTestContextCanceled_* tests (asset: 60s timeout lifecycle project)
• TimeoutWhenExpiresTests.cs — *_WhenTimeoutExpires_* and *_AttributeTakesPrecedence tests (asset: 1s timeout lifecycle project)
• TimeoutFromRunSettingsTests.cs — *_FromRunSettings_* tests (asset: no-timeout lifecycle project)
• TimeoutCooperativeCancellationTests.cs — CooperativeCancellation_* tests (asset: cooperative cancellation lifecycle project)
• TimeoutTestMethodTests.cs — Timeout_WhenMethodTimeout* tests (asset: [Timeout(1000)] on test method)
• TimeoutCooperativeTestMethodTests.cs — CooperativeTimeout_WhenMethodTimeout* tests (asset: [Timeout(1000, CooperativeCancellation = true)] on test method)

RunAndAssertWithRunSettingsAsync (which previously branched on two assets) was split into RunAndAssertAttributeTakesPrecedenceAsync and RunAndAssertFromRunSettingsAsync, each living in the class that owns the relevant asset.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Avoid having multiple test assets in a single test class</issue_title>
<issue_description>Continuation of #7552.

Overrides of GetAssetsToGenerate should have no reason to provide multiple assets. Having multiple assets means that all of these will be built during class initialize, reducing the ability to run more stuff in parallel, and forcing the build of irrelevant assets when running a single test that uses one of those assets. Currently, the only test class with multiple assets is test\IntegrationTests\MSTest.Acceptance.IntegrationTests\TimeoutTests.cs</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Avoid having multiple test assets in a single test class #7579

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[Copilot]

Pull request overview

Refactors the MSTest acceptance timeout integration tests to ensure each test class generates/builds only a single test asset, improving parallelism and reducing unnecessary asset builds during class initialization.

Changes:

• Split the former multi-asset TimeoutTests suite into multiple single-asset test classes.
• Kept TimeoutTests.cs focused on CLI --timeout parsing/behavior tests with a single TimeoutTest asset.
• Introduced dedicated classes/assets for timeout expiration, test-context cancellation, runsettings-based timeouts, cooperative cancellation, and method-level timeout scenarios.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/IntegrationTests/MSTest.Acceptance.IntegrationTests/TimeoutTests.cs	Reduced to the 5 CLI --timeout extension tests and a single TimeoutTest asset.
test/IntegrationTests/MSTest.Acceptance.IntegrationTests/TimeoutWhenCanceledTests.cs	New single-asset class covering *_WhenTestContextCanceled_* scenarios.
test/IntegrationTests/MSTest.Acceptance.IntegrationTests/TimeoutWhenExpiresTests.cs	New single-asset class covering *_WhenTimeoutExpires_* + attribute precedence scenarios.
test/IntegrationTests/MSTest.Acceptance.IntegrationTests/TimeoutFromRunSettingsTests.cs	New single-asset class covering runsettings-driven timeout behavior.
test/IntegrationTests/MSTest.Acceptance.IntegrationTests/TimeoutCooperativeCancellationTests.cs	New single-asset class covering cooperative cancellation lifecycle timeout behavior.
test/IntegrationTests/MSTest.Acceptance.IntegrationTests/TimeoutTestMethodTests.cs	New single-asset class covering [Timeout(1000)] on test method scenarios.
test/IntegrationTests/MSTest.Acceptance.IntegrationTests/TimeoutCooperativeTestMethodTests.cs	New single-asset class covering [Timeout(1000, CooperativeCancellation = true)] on test method scenarios.