Update and move 680-sink-regression into 639-checker-code-sinking

test/680-sink-regression was passing with and without its relevant
code so it wasn't working as a regression test. Move the relevant
bits out of it and into 639-checker-code-sinking which will fail
if we remove the relevant code from the codebase.

Bug: 226143661
Test: art/test/testrunner/testrunner.py --host --64 --optimizing -b
Change-Id: I4eac4852a0d6279bbe3ca8f041a27113d7d57be4
6 files changed