PR Summary

Fix the telemetry UUID cache mutex so each process acquires it exactly once and releases every acquired ownership path. The mutex is created with initiallyOwned: false, acquisition is bounded to 200 ms, and ownership transferred by AbandonedMutexException is tracked and released.

Add regression coverage for both concurrency cases: a telemetry-enabled holder process followed by an empty-cache child, and a child that must stop UUID creation when another process holds the named mutex past the acquisition timeout. Process completion is bounded to 15 seconds so a recurrence fails instead of hanging the suite indefinitely.

PR Context

Creating the named mutex with initiallyOwned: true acquires it immediately. Calling WaitOne() again recursively acquires the same mutex, while the existing cleanup called ReleaseMutex() only once. The process therefore retained ownership until exit and could block another telemetry-enabled shell indefinitely when that shell needed to recreate a missing UUID cache.

The acquisition state now also accounts for WaitOne() transferring ownership before throwing AbandonedMutexException. If acquisition exceeds 200 ms, UUID creation stops and telemetry is disabled for that process rather than blocking startup.

Validation:

• PowerShell parser: passed for test/powershell/engine/Basic/Telemetry.Tests.ps1.
• Local Pester 4.10.1: discovered 18 telemetry tests; all 18 were skipped because this Windows host's diagnostics policy disables PowerShell telemetry. The regression tests did not execute locally.
• Native Linux validation: ADO run 719777 (ReleaseAutomationTest-719777-ps) succeeded from Release-Automation SHA 2e97805a8732f12a8478ad06a4a97af885ccfed6, using PowerShell source release/v7.7.99-preview.94 at 9e1bf1694d95a1e684b20039720ba438a2e94606, coordinated build 719739, and package build 719755. Native x64 and ARM64 concurrent-holder/empty-cache children each completed in 3 seconds within a 20-second gate; the full elevated and unelevated suites reported 0 failures.
• Local product build was not run because this checkout pins .NET SDK 11.0.100-rc.1.26425.128, which is not installed on this host.

PR Checklist

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• Breaking changes
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• User-facing changes
  • Not Applicable
• Testing - New and feature
  • Make sure you've added a new test if existing tests do not effectively test the code changed