Cleanup "no panic support" tests

[jieyouxu]

There are a bunch of tests that say ignore-wasm or ignore-emscripten or ignore-$platform with a comment "no panic support" or "no panic". It would be good to audit them and see if one or more of the following capability-based conditional test execution directives can be used instead:

• //@ needs-unwind
• //@ needs-threads
• //@ needs-subprocess¹

If those are not sufficient, it would be good to improve the ignore reason anyway.

Footnotes

1. I'm still working on implementing this directive over at compiletest: add a needs-subprocess directive #128295. ↩

[jieyouxu]

Tagging as E-medium because this might involve running multiple try-jobs against certain CI jobs.

[yegeunyang]

@rustbot claim

[yegeunyang]

@rustbot release-assignment