Reland "Default to the threadsafe GTest death_test_style."

This is a reland of b579146695ba0c045d26b022e63d199bd23f8349

Original change's description:
> Default to the threadsafe GTest death_test_style.
>
> Using the default style of "fast" can lead to subtle test flakiness.
> And on macOS, most of CoreFoundation is not safe to use after fork()
> without exec(). Several //base implementations on Mac use CF, and so it
> is almost never safe to use the "fast" death_test_style.
>
> Change-Id: Idcee977978561e0a57ace20b53f597c566708692
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/570500
> Commit-Queue: Robert Sesek <rsesek@chromium.org>
> Reviewed-by: danakj <danakj@chromium.org>
> Reviewed-by: Gabriel Charette <gab@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#854588}

Change-Id: I6a30c23e5846b508ef0c1ab29a899c5a7b9f1293
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2747682
Reviewed-by: Sophie Chang <sophiechang@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#862111}

• base/test/test_suite.cc[diff]
• chrome/browser/optimization_guide/prediction/prediction_manager_unittest.cc[diff]
• third_party/crashpad/README.chromium[diff]
• third_party/crashpad/crashpad/test/multiprocess_posix_test.cc[diff]