Implement Sum-of-Abs-Differences idiom recognition.

Rationale:
Currently just on ARM64 (x86 lacks proper support),
using the SAD idiom yields great speedup on loops
that compute the sum-of-abs-difference operation.
Also includes some refinements around type conversions.

Speedup ExoPlayerAudio (golem run):
1.3x on ARM64
1.1x on x86

Test: test-art-host test-art-target

Bug: 64091002

Change-Id: Ia2b711d2bc23609a2ed50493dfe6719eedfe0130