Add data when sharing a tab

This CL adds data when sharing a tab:
- add the title as additional text that will be shared as a separate
  item. This is mapped to the attributedContentText and is used by
  most applications (including Gmail) as the title of the URL.
- Add LPLinkMetadata containing the same information as the URL shared
  object (title, URL, thumbnail). This can be used if multiple URL are
  shared.

Bug: 374746310
Change-Id: I7b063e16e55b367a49036c5b46b72d7e6ebc0d71
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6439511
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1444595}