Implement Mandatory Reauth confirmation bubble.

This bubble is displayed after the user has agreed to enable Mandatory
Reauth.

Screenshot:
https://screenshot.googleplex.com/A4Qvsi5r3s3THyD.png

Mockup:
https://screenshot.googleplex.com/4kPoTf8owipR3vL.png

Bug: 1427216
Change-Id: I5e2d32596ba08a2cc66e2f6bd1a594fbac91b90c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4499402


Commit-Queue: Justin Wells <justinleewells@google.com>
Reviewed-by: Vinny Persky <vinnypersky@google.com>
Cr-Commit-Position: refs/heads/main@{#1148009}