Hash-based DexCache methods array.

Total boot*.art size for aosp_angler-userdebug:
  - arm64:
    - before: 11603968
    - after: 10129408 (-1.4MiB, -12.7%)
  - arm:
    - before: 8626176
    - after: 7888896 (-0.7MiB, -8.5%)

Test: m test-art-host-gtest
Test: testrunner.py --host
Test: Nexus 6P boots.
Test: testrunner.py --target
Test: Build aosp_mips64-eng
Bug: 30627598
Change-Id: I7f858605de5f074cbd7f0d9c4c072fbd44aee28f