Add support for Baker read barriers in SystemArrayCopy intrinsics.

Add support for Baker read barriers in SystemArrayCopy intrinsics.

Benchmarks (ARM64) score variations on Nexus 5X with CPU
cores clamped at 960000 Hz (aosp_bullhead-userdebug build):
- Ritzperf - average (lower is better):       -3.03% (slightly better)
- CaffeineMark - average (higher is better):  +1.26% (slightly better)
- DeltaBlue (lower is better):               -10.50% (better)
- Richards - average (lower is better):       -3.36% (slightly better)
- SciMark2 - average (higher is better):      +0.26% (virtually unchanged)

Details about Ritzperf benchmarks with meaningful variations
(lower is better):
- FormulaEvaluationActions.EvaluateAndApplyChanges: -13.26% (better)
- FormulaEvaluationActions.EvaluateCascadingSums:   -10.94% (better)
- FormulaEvaluationActions.EvaluateComplexFormulas: -15.50% (better)
- FormulaEvaluationActions.EvaluateFibonacci:       -10.41% (better)
- FormulaEvaluationActions.EvaluateLargeSums:        +6.02% (worse)

Boot image code size variation on Nexus 5X
(aosp_bullhead-userdebug build):
- total ARM64 framework Oat files size change:
  107047632 bytes -> 107154128 bytes (+0.10%)
- total ARM framework Oat files size change:
  90932028 bytes -> 91009852 bytes (+0.09%)

Test: ART host and target (ARM, ARM64) tests + Nexus 5X boot.
Bug: 29516905
Bug: 29506760
Bug: 12687968
Change-Id: I85431368d09965687a0301ae2eb3c991f276ce5d