Feed all top-level GPU accessors through skgpu::BaseDevice

This pulls the GPU-specific accessors off of SkCanvas and SkDevice - moving them all to skgpu::BaseDevice and SkCanvasPriv.

This will allow us to more easily change the gpu class hierarchy (esp. changing GrSurfaceDrawContext to skgpu::v1:SurfaceDrawContext) w/o churning the public API.

Bug: skia:11837
Change-Id: I4e205255706680ac58ffe40f714884c2ee7ac799
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/431036
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
18 files changed