Fix and clean up field get/set entrypoints.

Fix `is_ref` argument for `*get_obj*` deoptimization.

Test: m test-art-host-gtest  # x86, x86-64
Test: testrunner.py --host --optimizing  # x86, x86-64
Test: testrunner.py --target --optimizing  # arm, arm64, riscv64
Bug: 283082089
Change-Id: I1f0c5e6233cb14c8b3c2149a756e8f72e84379e0
6 files changed