x86/x86-64: Rewrite `art_quick_aput_obj`.

Check for the GC marking just once and use a dedicated path
for GC marking on. Use `art_quick_read_barrier_mark_regNN`
for reference marking and remove the obsolete and slow
`READ_BARRIER` macros.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Test: testrunner.py --host --optimizing --gcstress
Bug: 160737021
Change-Id: I250e1bbeb5d93bc14055fc17d4eb0c6167c49e82
2 files changed