Adds a model & view layer for long screenshot tiles

An ImageTile wraps an Image with an attached HardwareBuffer,
as received from an ImageReader as used by scroll capture.

ImageTileSet provides a drawable to present the result on-screen,
TiledImageDrawable maintains a display list which is updated when
notified of a change. This object can also produce a Bitmap as
output for export to a compressed image.

This change also tightens up the ScrollCaptureClient interface
to internally define tile size and limits. Instead of accepted
arbitrary rectangles, accept only a single y-coordinate to
specify the verical position of the tile to capture.

Bug: 174571735
Bug: 148519342
Test: manually, take long screenshot
Change-Id: I81032766c33396f51cb117f87a4d65288990f66d