android-a11y: optimize scrolling by up to 50%

This change tests a hypothesis based upon logs.
Prefer scrolling first, then sending events to notify of accessibility focus changes.

Example scenario chromevox.com:
TalkBack moves from the first h1 to the next h3 (scrolling in the process)
Time of scroll to make visible
~100ms (before this change)
~49ms (with this change)

Turning off the java side cache
~180ms (before this change)
~49ms (with this change)

See go/clank-a11y-java-cache for more details.

R=mschillaci@google.com

Bug: b/417302062
Change-Id: I8b33165248101571254171911a39dcd385a0f424
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6634534
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Mark Schillaci <mschillaci@google.com>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1473216}