The previous setup of the test was suboptimal and could easily hide
bugs. Since the whole test body was wrapped in an ASSERT_DEATH call
(without checking any message of the crash), any CHECK failure inside
the test body would make the test pass.

This CL leverages the fact that in our setup the "death test style" is
set to "threadsafe" anyway, so the process that is forked for the death
test just runs the whole test body including the single death test of
interest, and the parent checks that it indeed crashes. This allows us
to undo our previous setup and just include death test assertions
regularly in the test body. By checking that the child process fails
exactly between two print statements (around the write access) we ensure
that we observe the crash we intend to observe.

R=jkummerow@chromium.org
CC=​mpdenton@chromium.org

Bug: v8:11974
Cq-Include-Trybots: luci.v8.try:v8_mac_arm64_rel_ng
Cq-Include-Trybots: luci.v8.try:v8_mac_arm64_dbg_ng
Change-Id: I293079ae2dbcbe154bef91314ed08cab567f4d18
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3151965Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76814}