PR Summary

Add codeanalysis attribute [DoesNotReturn] to ThrowTerminatingError

PR Context

Helps with code that has a return value but calls ThrowTerminatingError. Without it, code analysis suggests it is an error to not return a value in that code path.

PR Checklist

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• [ x] Summarized changes
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• Breaking changes
  • [x ] None
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  • Experimental feature(s) needed
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• User-facing changes
  • [ x] Not Applicable
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  • Documentation needed
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• Testing - New and feature
  • N/A or can only be tested interactively
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  • Make sure you've added a new test if existing tests do not effectively test the code changed
• Tooling
  • [ x] I have considered the user experience from a tooling perspective and don't believe tooling will be impacted.
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    • Impact on PowerShell Editor Services which is used in the PowerShell extension for VSCode
      (which runs in a different PS Host).
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    • Impact on Completions (both in the console and in editors) - one of PowerShell's most powerful features.
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    • Impact on PSScriptAnalyzer (which provides linting & formatting in the editor extensions).
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    • Impact on EditorSyntax (which provides syntax highlighting with in VSCode, GitHub, and many other editors).
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