try_par_for_each_in may have avenues for perf improvements

[oli-obk]

          This does look at bit expensive. It's probably a good idea to measure the performance impact of it. It might be a better idea to write the error to a mutex / atomic instead.

Originally posted by @Zoxc in #116849 (comment)

Once we have enabled parallel-compiler by default, we can run multithreaded benchmarks of the current impl against an impl that instead writes to an AtomicBool (as Result<(), ErrorGuaranteed> is effectively just a bool)

[Zoxc]

I measured the impact of the PR with 7 threads and it doesn't seem to have a significant impact.

Benchmark	Before	After
	Time	Time	%
🟣 clap:check:unchanged	0.5490s	0.5488s	-0.02%
🟣 hyper:check:unchanged	0.1674s	0.1674s	-0.01%
🟣 regex:check:unchanged	0.4109s	0.4120s	0.26%
🟣 syn:check:unchanged	0.7541s	0.7546s	0.07%
🟣 syntex_syntax:check:unchanged	1.8485s	1.8422s	-0.34%
Total	3.7298s	3.7250s	-0.13%
Summary	1.0000s	0.9999s	-0.01%