Prefer .ps1 than .cmd when both file exists in path

[balthild]

What new feature should Elvish have?

Currenlty on Windows, when both .ps1 and .cmd exists for a command (e.g. scoop), elvish will prefer invoking the .cmd.

However, cmd scripts are bad on UX. Specifically, It prompts "Terminate batch job (Y/N)" when Ctrl+C pressed. Therefore, it should be avoided if alternatives exists.

Output of "elvish -version"

0.21.0+official

Code of Conduct

• I agree to follow Elvish's Code of Conduct.

[xiaq]

There are a few workarounds to suppress the "Terminate batch job" prompt documented here: https://superuser.com/questions/1705792/how-to-suppress-windows-batch-job-termination-confirmation

[xiaq]

See my comment in #1854 about this feature request; I'm leaning towards rejecting this, but maybe it's a good idea to special-case .elv files on Windows instead.