Change the media search widget to work with resource queues and
providers. Create providers based on the user's filerepo settings
and aggregate their responses with the media queue. Stop asking
for more results from providers that are depleted.
Also fixes a rather nasty infinite-loop bug where the API returns
only very few images, and the UI keeps asking for more.
Bug: T78161
Bug: T88764
Change-Id: I65aed3446cd1f056476c56e6e04522c70e49e595
