[autofill] Implement the BNPL ToS controller

Implement the Buy-Now-Pay-Later Terms of Service controller to accept
and populate the view with proper data. In addition, hook in the
callback logic for accepting/cancelling the dialog. Add an additional
test that ensures that hitting the ESC key will also cancel the
dialog.

Bug: 391141123, b/378518066, b/356443046
Change-Id: Icc6172b9c2b9432140ab18a4306f1ecfbdde4172
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6318763
Reviewed-by: Slobodan Pejic <slobodan@chromium.org>
Reviewed-by: Vinny Persky <vinnypersky@google.com>
Reviewed-by: Jan Keitel <jkeitel@google.com>
Commit-Queue: Darwin Yang <darwinyang@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1429641}