This reverts commit 26a78061.

Reason for revert: Not all fuzzers support custom segfault handlers yet, see https://crbug.com/918949

Original change's description:
> Remove trap handler fallback for sanitizers
> 
> Since https://crrev.com/c/1335572, our sanitizers allow to set custom
> segfault handlers. Thus remove special code that was added to handle
> sanitizers that prevent installation of segfault handlers. Instead,
> CHECK that the signal handler was installed correctly.
> 
> R=​ahaas@chromium.org, mseaborn@chromium.org, mark@chromium.org
> 
> Bug: chromium:830894
> Change-Id: I3bd66e33efdceb3e8469f3f4a09fbde90cb3d7ec
> Reviewed-on: https://chromium-review.googlesource.com/c/1392199
> Reviewed-by: Andreas Haas <ahaas@chromium.org>
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#58513}

TBR=mseaborn@chromium.org,ahaas@chromium.org,mark@chromium.org,clemensh@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:830894, chromium:918949
Change-Id: Ide545860cf7729139ac50c0dd2e85facca49b0b1
Reviewed-on: https://chromium-review.googlesource.com/c/1396277Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58556}