jobqueue: migrate root job deduplication to the WAN cache

jobqueue: migrate root job deduplication to the WAN cache

If the root job timestamp keys are lost or otherwise unknown, they
will now be deductively recached with the best known values as jobs
are popped and executed. This means the running any of many child
jobs of a root job can restore the root timestamp if it was lost.
This does not need to use the main stash given this fact.

Bug: T227376
Change-Id: Iae0f3af15803af048ff49f3bf281b2bde18c87f2