Update app compilation APIs.

- Add performance characteristics to `optimizePackage`.
- Add a link to the compiler filter spec. (Note that the doc is currently
  a bit outdated, but the doc updates are submitted and staging, so the
  doc will eventually be up-to-date.)
- Make constants in ReasonMapping public.

This CL doesn't include changes to PriorityClassApi because the
suggested changes are still under discussion.

Bug: 246854668
Test: m com.google.android.art
Ignore-AOSP-First: ART Services.
Change-Id: I0676b4ce18e8deee98b0047465965be85782804f
4 files changed