Misc skgpu cleanup

This CL:
  finishes off some renaming I missed earlier
  removes some extraneous #includes from headers

TBR=bsalomon@google.com
Bug: skia:11837
Change-Id: If7163435a44d4067dac041a7f9e68b1ad63432d0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/426037
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
8 files changed