Simplifications to GrTextureProducers

Move all MIP map code directly into GrTextureAdjust, not used by makers.

Make GrTextureAdjuster final.

Make some virtuals private

Change-Id: I12dc7d8fa015dc85aaca3f7d5e58e094bb859518
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/274045
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
8 files changed