Android R Preview 4 (RPP4.200409.015)
Merge mirror-aosp-master `prebuilts/runtime` into stage-aosp-master.

The stage-aosp-master revision of `prebuilts/runtime` was way behind
its mirror-aosp-master counterpart, creating build failures.

There is no automatic merge path from mirror-aosp-master to
stage-aosp-master for this project yet, but this is being worked
on (b/147283805). Actually, the CL implementing that feature
(https://android-review.googlesource.com/c/platform/manifest/+/1201852)
is being blocked in presubmit testing by `prebuilts/runtime` being too
old.

Test: Run these commands:
        . ./build/envsetup.sh \
          && lunch sdk-eng \
          && art/tools/buildbot-build.sh --host
      on an Android (internal) master-art source tree.
Bug: 139131024
Bug: 144702219
Bug: 147283805
tree: 6843c8648c0dda8f589f4a5fce2221c486bfcbfb
  1. appcompat/
  2. common/
  3. adb
  4. Android.mk
  5. update.py