[graphite] Move pipeline caches to GlobalCache

Change-Id: I9e9b054f0a36dd0c5365e38cb19eb94199014ae3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/568580
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
6 files changed