[A11y] Don't try to hyper-optimize role changes

Attempts to avoid removing/rebuilding the subtree after a role change
could lead to unpredictable code paths for computations that rely
on parent properties such as the role. The previous code may have
helped lead to crashes by trying to be "too clever".

This is a follow-up to CL:5616990. A downstream CL works on the
problem further.

Bug: 346158514
Change-Id: Iba0006ca12e7f6746877b182246260539e2ca6b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5621870


Commit-Queue: Benjamin Beaudry <benjamin.beaudry@microsoft.com>
Reviewed-by: Benjamin Beaudry <benjamin.beaudry@microsoft.com>
Auto-Submit: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1313523}