[iOS] Create the TableView link footer

This CL creates a TableView item for handling a footer which would
display a link in a TextView.
This is designed as a replacement for CollectionViewFooterItem.

Bug: 894791
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: Id4b84e5b17920237016314447bed9a25140ab30c
Reviewed-on: https://chromium-review.googlesource.com/c/1286416
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600717}
4 files changed