Preview UI: specify metadata columns, change metada reading order

Specify columns passed to ContentResolver#query.
Read ContentResolver#getStreamTypes before ContentResolver#query because
if the former returns, among others, an image mime types we can avoid
reading the latter.

Bug: 279674836
Test: unit tests, manual testing wiht Drive and a Photos prototype.
Change-Id: Ide31f5c9aae21c9e0ce93bec9a8d829851532f4a
2 files changed