Move the remainder of GrRenderTargetContext factories.

This mostly handles cases where we are wrapping a GrBackend* or an already
made proxy.

Change-Id: Ieb33eb51f7db84611ade0f8243b6d9023ce8e390
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/262234
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
12 files changed