Dump init stacks when aborting either due to LOG(FATAL) or in
userdebug/eng builds due to signals, including signals from
sanitizers.
Doesn't work for static first stage init yet, b/133450393 tracks
that.
Also, ensure that LOG(FATAL) in child processes calls abort() in all
stages of init, not just 2nd stage init.
Bug: 131747478
Test: abort init in various ways and see stacks
Test: hang or crash in backtrace handler and see child reboot
Change-Id: Ib53b5d3e7e814244203f875de016ada9900dfce8
Merged-In: Ib53b5d3e7e814244203f875de016ada9900dfce8
(cherry picked from commit 59656fb377)
This is a baseline for splitting init first and second stage into
their own executables.
Bug: 79758715
Test: sailfish boots
Change-Id: I549ad4502893b3a5e4c2a9886f66850f6d31b619
