ARM64: Heap poisoning for link-time Baker CC read barrier thunks.

And fix running out of scratch registers for HArraySet
with large constant index and a reference to poison.

Test: Nexus 6P boots with heap poisoning enabled.
Test: testrunner.py --target with heap poisoning enabled on Nexus 6P.
Bug: 29516974
Bug: 30126666
Bug: 36141117
Change-Id: Ifb38f4a0e23a2963468772f34f294febfc340b8c
4 files changed