Reactivate closed-issue Extensions tests

[svick]

Summary

• Reactivates the Microsoft.Extensions test cases listed in Reactivate ActiveIssue tests in Microsoft.Extensions where the issue is no longer active #131327 whose ActiveIssue references point to closed issues.
• Removes associated project-level CI exclusions so the cases are actually exercised.
• The five configuration reload cases associated with Using FileWatcher on non-windows has a very large impact on startup time #42036 were already active on current main.
• Keeps MessageTests_SuppressWarning_WarnAsError_NoError disabled because reactivating roslyn#52527 reproduces 12 SYSLIB1015 build errors locally before tests can run.

Current purpose

This draft PR currently exists to run the full CI matrix and determine which reactivated cases are reliable on supported configurations. Any reactivated test that fails for any reason will be disabled again, with failure details recorded in a PR comment, before another CI run.

Local validation

The libraries baseline build and the affected desktop test projects pass with the known roslyn#52527 case kept disabled.

Contributes to #131327

Note

This PR description was generated with GitHub Copilot.

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[svick]

CI run 1 (runtime build 1566711) showed that three reactivated browser scopes are still problematic, so commit 4ea5354d596 disables them again:

• Microsoft.Extensions.Caching.Memory.Tests assembly — failed on Chrome/Firefox with Mono and Chrome with CoreCLR, on Linux and Windows browser queues. Each run had 19–25 failing tests, including unsupported operations and assertion failures. Example work items: Chrome/Mono on Windows, Firefox/Mono on Linux, and Chrome/CoreCLR batch.
• Microsoft.Extensions.DependencyInjection.ExternalContainers.Tests assembly — 63 tests failed per browser run, primarily with System.PlatformNotSupportedException: Operation is not supported on this platform, on Chrome/Firefox with Mono and Chrome with CoreCLR. Example work items: Chrome/Mono on Linux and Chrome/CoreCLR batch.
• XmlConfigurationTest.LoadKeyValuePairsFromValidEncryptedXml — failed on browser Mono and CoreCLR with System.PlatformNotSupportedException: Algorithm 'Aes' is not supported on this platform. Example work items: Chrome/Mono on Linux and Chrome/CoreCLR batch.

The linker and inner-loop pipelines passed. All runtime failures were accounted for by these reactivated scopes; no unrelated failure was found.

Note

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[svick]

/azp run runtime, runtime-dev-innerloop, dotnet-linker-tests

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Azure Pipelines:
Successfully started running 3 pipeline(s).

[svick]

/azp run runtime, runtime-dev-innerloop, dotnet-linker-tests

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).

[svick]

/azp run runtime, runtime-dev-innerloop, dotnet-linker-tests

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).