[ios] Add a Lens Promo for use with the Lens Tips Notification

Screencast of promo:
http://screencast/cast/NjI2Mzg1NTY0NTcyMDU3Nnw0YmZmNmRlYS1hNw

Fixed: 361817967
Change-Id: Iad6a1f0368860aab619586dd786292e22f048642
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5824280


Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Scott Yoder <scottyoder@google.com>
Cr-Commit-Position: refs/heads/main@{#1349243}