Decode one row of tiles at a time for image that has tiles

Add an api to IMediaMetadataRetriever to decode image rect.
It will reuse the same full frame IMemory, and decode only
the requested rect. For now, StagefrightMetadataRetriever
will only allow decoding of rect that's a full row of tiles,
and the requested must be issued sequentially (i.e. no
arbitrary rects). When the extract side is fixed to allow
seeking by tiles, it can be extended to allow arbitrary
rects.

This allows HeifDecoderImpl (on client side) to start
processing the getScanlines in parallel with the decoding.

Test: CTS MediaMetadataRetrieverTest;
Manual testing of HEIF decoding of files with or without tiles;
Manual testing of HEIF thumbnails generation in Downloads app.

bug: 78475896
Change-Id: I820b21cdf33f80593ee6092d8e1ba68b3beb65dd