PR Summary

The previous code was always completing the progress between file copies so if you're just copying a folder of files, then the progress gets cleared quickly or before it shows so it appears that no progress is rendering. Fix is to only complete the progress if all the files have been copied.

PR Context

Fix #19600

PR Checklist

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• Breaking changes
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  • Experimental feature(s) needed
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• User-facing changes
  • 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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• Tooling
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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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