[lensoverlay] Fix context menu showing after action taken.

Adds a new event to the selection overlay for updating the selected
region context menu options instead of forcing it to show. Make sure the
simplified text layer does not show the region context menu more than
once per region selection.

Change-Id: I83030c9c37b3c99e8b4247f4cb888f5a2d0c62f0
Bug: 405420174
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6393797
Reviewed-by: Ali Stanfield <stanfield@google.com>
Auto-Submit: Juan Mojica <juanmojica@google.com>
Commit-Queue: Ali Stanfield <stanfield@google.com>
Cr-Commit-Position: refs/heads/main@{#1438349}