Make delete more robust (fix #1662)

[o-l-a-v]

PR Summary

Make delete more robust by trying multiple times before failing, to fix #1662.

PR Context

In #1662 I experienced that PSResourceGet would fail to install modules because antimalware realtime scanners added file handles on files inside %TEMP% that were to be deleted.

I read here https://stackoverflow.com/a/329502/9874541 that trying multiple times is a common approach for scenarios like these.

I then tried adapting the existing code to try multiple times on the step that sometimes failed.

I tried the code by building both net472 and netstandard2.0, and I could no longer reproduce #1662.

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[o-l-a-v]

I'm no C# expert, I've tried my best to make the delete directory function more robust by trying multiple times. Source of inspiration:

• https://stackoverflow.com/questions/929276/how-to-recursively-list-all-the-files-in-a-directory-in-c

I've also tried to read up on the best way to wait a little between attempts. It's my understanding from what I've read that if function is not async, Thread.Sleep() is fine.