Start paving the way for XMP metadata.

The Extensible Metadata Platform (XMP) standard is widely used to
annotate useful information about audio, video, and image files, so
this change starts indexing certain widely-useful fields.

For example, the "document ID" concept is designed to uniquely
identify media items regardless of renaming or trivial metadata
edits over time.  And "original document ID" gives a clean way of
identifying a chain of derivative works.

Finally, the "format" attribute can be used to specify a richer MIME
type that may not be recognizable from a file extension alone.

While we're making changes here, remove several APIs that we've
realized aren't needed for Q, such as "trashing."

Bug: 120791890
Test: atest MediaProviderTests
Test: atest cts/tests/tests/provider/src/android/provider/cts/MediaStore*
Change-Id: I0361dd857aed4c2e2f533685478db1c558a97564