runtime: add thread exit plus vgetrandom stress test
Add a regression test similar to the reproducer from #73141 to try to
help catch future issues with vgetrandom and thread exit. Though the
test isn't very precise, it just hammers thread exit.
When the test reproduces #73141, it simply crashes with a SIGSEGV and no
output or stack trace, which would be very unfortunate on a builder.
https://go.dev/issue/49165 tracks collecting core dumps from builders,
which would make this more tractable to debug.
For #73141.
Change-Id: I6a6a636c7d7b41e2729ff6ceb30fd7f979aa9978
Reviewed-on: https://go-review.googlesource.com/c/go/+/662636 Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Pratt <mpratt@google.com>