This CL adds an internal method to copy textures, that will disregard
the need of having CopySrc usage.
This CL adds an intermediate helped method to be used by both
APIContextTextureToTexture and APIContextTextureToTextureInternal.
Fixed: dawn:1052
Change-Id: Icd28e0ef58ecfaa412eefe8c95e41cd2298a9acc
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/58440
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Juanmi Huertas <juanmihd@chromium.org>