[graphite] Rename clip shader block to be more generic.

This allows us to use it for analytic clips as well.

Bug: b/238762307
Change-Id: I58a14f7b8058c1573a69aa0b59e435700e585dbc
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/895736
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
6 files changed