Let RWHVA observe ViewAndroid removal from hierarchy

As per current logic RenderWidgetHostViewAndroid(RWHVA) is removed from
ViewAndroid observers before ViewAndroid is detached from hierarchy.
As a result some of the cleanup code in RWHVA::OnDetachedFromWindow never
gets to run.

With this change we are conditionally doing it in case
InputVizard is enabled, this is done to do a safe cherrypick to an
earlier mileston, in a followup change we will remove the conditional
and will always remove parent before removing RWHVA from observers list.

Bug: 440324557
Change-Id: I4893b88d2280a2d670a31e155b93ae2f86ab07f9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6927311
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Kartar Singh <kartarsingh@google.com>
Cr-Commit-Position: refs/heads/main@{#1513311}