[Clank] Integrate loading url with spare tab

This CL implements logic to handle loading url using the spareTab.
This is integrated with CreateNewTab where we check if a spare
tab is available before creating a new one for loading a url.

To allow loading url in A spare tab, which requires reparenting the parent. We add new helper method Tab.reparentSpareTab(Tab parent).

Detailed design doc for spare tab optimization:
https://docs.google.com/document/d/1blqCc7W8oGNtKVn90yLJDYUWSqzoO03aE5tyk1CrWLM/edit?usp=sharing&resourcekey=0-qj1ZVcaqm2s3vOR2eEQqJA

BUG=1412572

Change-Id: Ib61dbb33fe64c7114e98906442dca8a9c218171f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4415678
Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Sreeja Kamishetty <sreejakshetty@chromium.org>
Code-Coverage: Findit <findit-for-me@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1134038}