runtime: deflake CGO traceback tests
runtime: deflake CGO traceback tests

The CGO traceback function is called whenever CGO code is executing and
a signal is received. This occurs much more frequently now SIGURG
is used for preemption.

Disable signal preemption to significantly increase the likelihood that
a signal results in a profile sample during the test.

Updates #37201

Change-Id: Icb1a33ab0754d1a74882a4ee265b4026abe30bdc
Reviewed-on: https://go-review.googlesource.com/c/go/+/219417
Run-TryBot: Emmanuel Odeke <277f8eaa8c7dfbc55c17bf5e30561c1a9c45c569@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

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