-Z panic_abort_tests does not support #[bench]

[tmandry]

If we try to run a test binary built with -Z panic-abort-tests and that test has a function with the #[bench] attribute, the binary will panic with the following error:

thread 'main' panicked at 'Cannot run dynamic test fn out-of-process', library/test/src/lib.rs:549:22

This is because we convert #[bench] to a test using DynTestFn when not running benchmarks, but DynTestFn is not supported with -Z panic-abort-tests, because we must run tests out of process and don't have a way to pass a closure to another process.

[ehuss]

I think this may be a duplicate of #73509?

[tmandry]

Yep, thanks.