Move stream based EXIF support to DocsProvider

@hide for now. Basically any client with stream for a file (advised to be local resource) can get standard metadata.
In FileSystemProvider, include METADATA SUPPORTED flag for image files.

Bug: 63893154
Test: build and test interactively.
Change-Id: Idc6fecd53625b108647d66a45ac115a945a1083c
2 files changed