PR Summary

Re-enabled the existing Clipboard code for Windows which relies on the Clipboard class from WinForms. For Linux, it requires xclip and macOS pbcopy and pbpaste. Had to #ifdef out a bunch of code that only works on Windows for copy/pasting non-text types. On Linux/macOS, decided to retain the parameters even if not supported to provide a more detailed error message.

Had to modify typegen as one of the types in Winforms being used has no HashAlgorithm so typegen threw. Instead, it skips assemblies where no HashAlgorithm is used which appears to only be an Accessibility assembly associated with WinForms.

To support win-arm builds, creating new WINFORMS def in csproj and uses clip.exe to set the clipboard, but no cmdline tool on win-arm to get contents of clipboard so had to disable all tests on win-arm since it depends on getting content out.

To support PSXunit tests, default to Microsoft.NET.Sdk if SDKToUse is not explicitly defined.

PR Context

Fix #4307

PR Checklist

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• Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
• This PR is ready to merge and is not Work in Progress.
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• Breaking changes
  • None
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  • Experimental feature(s) needed
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• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed Add back content for clipboard cmdlets MicrosoftDocs/PowerShell-Docs#4628
    • Issue filed:
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  • 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
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