runtime: execute TestSpuriousWakeupsNeverHangSemasleep in parallel
runtime: execute TestSpuriousWakeupsNeverHangSemasleep in parallel

This test spends most of its time sleeping and waiting on a subprocess
to sleep. It seems like a prime candidate to run in parallel, although
we may need to relax its hard-coded 2s timeout on the sleep(1)
subprocess.

For #48770

Change-Id: I4e839739fe82446615f9894c1904c87e5f3cf386
Reviewed-on: https://go-review.googlesource.com/c/go/+/366256
Trust: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Run-TryBot: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Reviewed-by: Emmanuel Odeke <bd234ba4276433f0e5fc7a8fa2d18274fa711567@orijtech.com>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

cloudflare/go,golang/go,cloudflare/go,golang/go,cloudflare/go,CAFxX/go,CAFxX/go,golang/go,nawawi/go,golang/go,nawawi/go,golang/go,CAFxX/go,nawawi/go,CAFxX/go,nawawi/go,cloudflare/go,cloudflare/go,nawawi/go,cloudflare/go,nawawi/go,nawawi/go,cloudflare/go,golang/go,golang/go,golang/go,CAFxX/go,CAFxX/go,nawawi/go,CAFxX/go,cloudflare/go,CAFxX/go