Revert "Revert "Use implicit null checks inside try blocks.""

Fix implicit checks in try blocks to emit stack maps.
Fix arm64 null expection from signal entrypoint to call
the runtime handler instead or simply jumping there.

On Nexus 9, AOSP ToT, the boot.oat size reduction is
  prebuilt multi-part boot image:
    - 32-bit boot.oat: -448KiB (-1.3%)
    - 64-bit boot.oat: -528KiB (-1.2%)
  on-device built single boot image:
    - 32-bit boot.oat: -448KiB (-1.4%)
    - 64-bit boot.oat: -528KiB (-1.3%)
Note that the oat files no longer contain dex files which
have been moved to vdex, so the percentages are not directly
comparable with the those reported in the original commit.

Test: Run ART test suite including gc-stress on host and Nexus 9.
Bug: 30212852
Bug: 31468464

This reverts commit 0719b5b9.

Change-Id: If8a9da8c11adf2aad203e93b6684ce16ed776285