runtime: add debugging to TestTimePprof
runtime: add debugging to TestTimePprof

We've seen timeouts of TestTimePprof, but the tracebacks aren't useful
because goroutines are running on other threads. Add GOTRACEBACK=crash
to catch these in the future.

For #41120.

Change-Id: I97318172ef78d0cbab10df5e4ffcbfeadff579e3
Reviewed-on: https://go-review.googlesource.com/c/go/+/258802
Trust: Austin Clements <7ea35d812706d9213868749011af1ed4fa2f6aa0@google.com>
Run-TryBot: Austin Clements <7ea35d812706d9213868749011af1ed4fa2f6aa0@google.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>

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