Revert^2 "ARM: Reimplement the UnsafeCASObject intrinsic."

This reverts commit f28be439.

The regression test for the revert reason was added in
    https://android-review.googlesource.com/731508 .
We fix the problem by introducing a specialized entrypoint
for the UnsafeCASObject intrinsic introspection marking
where we read the destination register from the right bits.

Change-Id: I1838abe05474be009d0fd96125efebd7f6dd9c59
Test: m test-art-host-gtest
Test: Pixel 2 XL boots.
Test: testrunner.py --target --optimizing --32
Test: ART_HEAP_POISONING=true testrunner.py --target --optimizing --32
Bug: 36141117