[graphite] Hook up text renderers.

Sets up the matrix that transforms the SubRun data to device space,
and adds a method to get the correct Renderer for a SubRun.

Bug: skia:13118
Change-Id: I6d478af02a5e21635a7ed6c49f1c2a0649937f8b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/553524
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
14 files changed