Use -File to improve pwsh exit status
What does this MR do?
It allows pwsh jobs with FF_DISABLE_POWERSHELL_STDIN, and switches powershell/pwsh jobs with that feature flag to use (shell) -File instead of (shell) -Command.
Why was this MR needed?
The -Command flag causes powershell to convert all non-zero exit statuses to exit(1); so if a script command has a unique and interesting exit status, that information was being lost. This is bad for jobs that want to take advantage of allow_failure exit codes.
What's the best way to test this MR?
Submit CI jobs with different command failure exit statuses, ensuring that the final exit status is as expected.