Migrate last public API to GrDirectContext

Cut & paste with some reorganization of includes & forward-decls.

Next up is GrContextPriv.

Change-Id: I72d2d95c62692e3b37608517b796c0041ffedea3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/326157
Reviewed-by: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Adlai Holler <adlai@google.com>
4 files changed