x86_64: Implement VarHandle.get{,Acquire,Opaque,Volatile} for byte array views.

Benchmarks improvements (using benchmarks provided by
https://android-review.googlesource.com/1420959):

  benchmark                              before   after
  -----------------------------------------------------
  VarHandleGetByteArrayViewInt             2.74   0.002
  VarHandleGetByteArrayViewBigEndianInt    2.74   0.003

Bug: 71781600
Test: lunch aosp_cf_x86_64_phone-userdebug \
  && art/test.py --host -r -t 712-varhandle-invocations --64
Test: Repeat with ART_USE_READ_BARRIER=false.
Test: Repeat with ART_HEAP_POISONING=true.
Change-Id: I4974b5773efb15b6245f690575218536d2c514db
5 files changed