Scripts: How to escape paths for command line

[mstv]

Before the changes were made for SelectedFiles to return a blob path rather than full-path I've been making changes so I could concat/replace/etc these variables via "Run on PowerShell" option and one of the problems I ran into is that this kind of escaping did not work.

So I went to see how ProcessStartInfo does it and it was different than current method. When I changed current method to what's used in the BCL, then the test-cases for WSL and Windows became identical. Could you look at this commit to see what I mean: mdonatas@768ca88

Basically I think we can unify these two methods esp. given that current method did not work when running with PowerShell mode.

Originally posted by @mdonatas-trafi in #11795 (comment)

[mstv]

@mdonatas, please come to an agreement with @SlugFiller. I do not have a strong opinion myself because I hardly encounter files which need escaping.

[SlugFiller]

The version I made is based on my experiments on what actually executes, e.g. when passed as parameter to cmd /c. If the patch checks out in practice (i.e. Executing with System.Diagnostics.Process), then I have no nitpicks about the specifics of the escaped output.