[BNPL][Clank] Create footer terms UI for BNPL screens

This CL adds the footer terms for the Buy Now, Pay Later (BNPL) issuer
selection and progress bottom sheet. The footer terms is a string:
"Payment plans are subject to eligibility."

Implementation: https://screenshot.googleplex.com/6rp45FTvuY57cdc.png
Mock: https://screenshot.googleplex.com/5nmT6WAGrfgquVk.png

Design: go/autofill-clank-bnpl

Bug: 430575808, b:438784405
Change-Id: I58ae6dbffa75c6463ef208daf6ad35b9259c0b3f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7043284
Reviewed-by: Vinny Persky <vinnypersky@google.com>
Commit-Queue: Fernando Ramirez <ferny@google.com>
Reviewed-by: Timofey Chudakov <tchudakov@google.com>
Cr-Commit-Position: refs/heads/main@{#1530372}