Recognize Clipboard Search suggestions as Search types.

This change ensures Clipboard suggestions are correctly categorized as
either URL (CLIPBOARD_URL) or Search (CLIPBOARD_TEXT,
CLIPBOARD_IMAGE).

The Search clipboard types feature custom description: (Text you
copied / Image you copied), but for the sake of completeness, this
change ensures that the keyword field is also populated.

The change ensures that Clipboard text and image suggestions do not
show up if the text/image searches are not supported by the template
url, or are blocked by policy.

Bug: 1468402
Change-Id: Id55fe397c9d58d6c7ae1c3bd7b05ad08058b431e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4744064
Reviewed-by: Patrick Noland <pnoland@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1179409}