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