Move all YUVA image creation in GMs into sk_gpu_test::LazyYUVImage.

LazyYUVImage now supports making images from a generator and from
textures. It uses ManagedBackendTexture to manage texture plane
lifetime via ref-counting.

Adds some supporting utility functions to SkYUVAInfo and
SkYUVAPixmaps.

Eases transition of forthcoming MakeFromYUVATextures API change.

Bug: skia:10632

Change-Id: I8cfd747c27076d1627da6ea8a169e554a96049e0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/326720
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
14 files changed