Auto merge of #144305 - ChrisDenton:win-free-disk-space, r=marcoieni

Free disk space on Windows 2025 runners

I've managed to reduce the time deletion takes by:

 - Using powershell, which is generally faster for filesystem operations than msys2
 - Performing deletions concurrently then waiting for them all to complete

It still takes 2-10 mins but that's not too bad.

Author: bors