[ios] Add WebState::GetLastActiveTime()

Add the notion of "last active time" to WebState (mirroring
the same notion in content::WebContents). The time reflects
the last time the WebState become visible.

Convert ShoppingPersistedDataTabHelper and TabUrlProviderImpl
to use "last active time" instead of checking the timestamp
of the last committed item (as an approximation of the last
active time).

Save and restore the "last active time" when saving the session
as we do not want the value to be cleared if the OS decides to
kill Chrome while it is suspended.

Force the "last active time" to "now" when cloning a WebState
during "preload" or "link preview" features.

Bug: 1238043, 1291626
Change-Id: I70f5b2d05af4e4422a4a9e3e4efb21a9f076ace0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3440215


Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/main@{#968343}