Add traces and timeout for node shutdown

[YuliiaKovalova]

This PR helps with diagnosing and potentially working around a problem where nodes don't signal completion due to crash reason: https://developercommunity.visualstudio.com/t/Canceling-build-failed-no-path-to-conti/10933619

The selected timeout is 5 seconds, but we can extend/cut it.

[Copilot]

Pull Request Overview

This PR adds tracing events for node shutdown success/failure and implements a timeout when waiting for node shutdown in EndBuild to prevent indefinite hangs.

• Introduce a _nodesShutDownSuccessfully flag and use WaitOne(TimeSpan.FromSeconds(5)) in EndBuild, logging failures on timeout.
• Add NodeShutdownFailure and NodeShutdownSuccess events to MSBuildEventSource and emit them when nodes shut down.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
MSBuildEventSource.cs	Add NodeShutdownFailure and NodeShutdownSuccess event methods.
BuildManager.cs	Use timed wait for node shutdown, log failure/success events, add _nodesShutDownSuccessfully.

Comments suppressed due to low confidence (4)

src/Build/BackEnd/BuildManager/BuildManager.cs:272

• The XML comment for _nodesShutDownSuccessfully is vague and describes it as a debugging property. Update it to explain the flag’s purpose (i.e., whether all nodes shut down within the timeout).

        private bool _nodesShutDownSuccessfully;

src/Framework/MSBuildEventSource.cs:683

• The new NodeShutdownFailure event lacks an XML doc comment. Add <summary> and <param> tags to describe the event semantics and the additionalInformation parameter.

        [Event(94, Keywords = Keywords.All)]

src/Framework/MSBuildEventSource.cs:689

• The new NodeShutdownSuccess event is missing documentation. Include an XML comment to explain when it’s emitted and the meaning of its parameter.

        [Event(95, Keywords = Keywords.All)]

src/Build/BackEnd/BuildManager/BuildManager.cs:272

• Storing this state in a private field risks carrying over the value between builds. Consider making it a local variable in EndBuild or resetting it at the start of each build.

        private bool _nodesShutDownSuccessfully;