Remove post-GC verification and other intentional delays

Now that the userfaultfd GC is stable enough, remove the delays caused
by post-GC verification and the delay we intentionally put between
marking and compaction phase.

These are probably causing timeout in ThreadStress.

Bug: 264353910
Test: art/test/testrunner/testrunner.py --target -t 004-ThreadStress
Change-Id: I47a51574aa8673f66e8dccd24a6e41b1eb400239
1 file changed