Shuffling to prepare for MediaProvider APEX.

An upcoming change will move MediaStore to be within the recently
created MediaProvider APEX.  This means that MediaStore will need to
be fully built against @SystemApi, and so this CL adjusts APIs to
support a clean transition:

-- Listing of "recent" storage volumes and scan paths for "internal"
storage is now handled by StorageManager directly, so that partners
retain control over what is deemed recent.
-- StorageVolume now returns the MediaStore volume name and the
filesystem directory where its contents are presented to apps.
-- Conversion of legacy thumbnail "kind" values to dimensions now
happens directly inside MediaStore.
-- PendingParams and PendingSession are completely removed.
-- Contributed media APIs are completely removed.
-- Media for demo users is now surfaced as a unique StorageVolume.
-- Migrate most MediaStore APIs to accept ContentResolver, which
supports easy usage of ContentResolver.wrap().

Bug: 144247087, 137890034
Test: atest --test-mapping packages/providers/MediaProvider
Exempt-From-Owner-Approval: in-place refactoring
Change-Id: I445528b2779bb37b9f2558e67a3cfc9f60412092