Convert GrManyDependentsMipMappedTest to a mock gpu test

This allows us to test with fReduceOpListSplitting both enabled and
disabled.

This CL also requires adding basic mipmap support to GrMockGpu.

Bug: skia:
Change-Id: I97ba912a9e5f3b90756c027ac19c003c99c15902
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/235996
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
6 files changed