[graphite] Add support for finished callbacks.

This also reworks a little bit about what we send to insertRecording
and what we store on Context.

Bug: skia:12974
Change-Id: I747a1cdd1559d4d5fbe928e689a23a734142557b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/524012
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
16 files changed