We've already been parsing them for many years, and they're well
defined by other public APIs, so let's reveal them in MediaStore.
Also get some storage-related documentation updated to guide
developers towards replacements in a post-scoped-storage world.
Bug: 140247264, 139185855, 141523097, 139185322
Test: atest --test-mapping packages/providers/MediaProvider
Change-Id: Id39a74a9972a330b3f83913b2eef5100ec59627d