Move GrContextOptions to GrContext_Base and make GrContextThreadSafeProxy be derived from GrContext_Base

The main thrust of this CL is to bring the GrContextThreadSafeProxy into the fold.

Change-Id: I8f457d5b75c69f89beac3a0035b1c05ba5d3b931
Reviewed-on: https://skia-review.googlesource.com/c/188622
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
24 files changed