Merge "Expose Handler APIs as @TestApi" into main am: af34323431 am: 181d41ec3a

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/3404741

Change-Id: Ib9d1b2fb16b4f73d4f30eae94bb9c43963e9c773
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>