Add stress-test for spurious failures of RMW operations.
The test `$noinline$testUnsafeReferences()` catches the bug
fixed by
https://android-review.googlesource.com/1924397 .
Test: 183-rmw-stress-test
Bug: 218453177
Change-Id: I1f439a54e03ff8e433b80f63ebb5c41a14bdb1dd