Add descriptive names to MSBuild thread instances for debugging and performance tracing

[Copilot]

Context

MSBuild creates numerous threads across different components. Without descriptive names, debugging multithreaded builds and analyzing performance traces requires correlating thread IDs with source code, which is time-consuming and error-prone. Most threads already had names, but two critical schedulers were missing them.

Changes Made

Added thread naming to the two remaining unnamed thread creation sites:

• RequestBuilder's DedicatedThreadsTaskScheduler: Names threads as "MSBuild RequestBuilder Task Scheduler Thread {id}" for task execution scheduling
• AwaitExtensions' OneSTAThreadPerTaskScheduler: Names threads as "MSBuild STA Task Scheduler Thread {id}" for STA-required task execution

Both implementations use Interlocked.Increment for thread-safe ID generation.

// RequestBuilder.cs
private int _threadCount = 0;

private void InjectThread()
{
    int currentThreadId = Interlocked.Increment(ref _threadCount);
    var thread = new Thread(() => { /* ... */ });
    thread.Name = $"MSBuild RequestBuilder Task Scheduler Thread {currentThreadId}";
    thread.Start();
}

Testing

• Full build passes
• RequestBuilder unit tests pass
• Sample project builds work correctly

Notes

All MSBuild threads now have descriptive names. The existing 10 named thread types remain unchanged.

Original prompt

there are a bunch of threads utilized in MSBuild, give them descriptive names so tracing perf and debugging is easy. Especially i'm interested in in-proc node threads that build the projects in multithreaded mode, but analyze and name other cases too

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