Make stencils be attachable to render targets created via SkSurface::MakeFromBackendT...

Make stencils be attachable to render targets created via SkSurface::MakeFromBackendTextureAsRenderTarget

This is a regression from "Refactor to separate backend object lifecycle
and GpuResource budget decision".

GrGLRenderTarget::CreateWrapped creates only render targets that wrap
the FBO.
GrGLRenderTargetTexture::CreateWrapped creates render targets that
wrap the texture.

Use the latter as the implementation for
SkSurface::MakeFromBackendTextureAsRenderTarget.

The test contains disabled code. The
MakeFromBackendTextureAsRenderTarget does not copy the existing texture
contents to the FBO render buffer.
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Review-Url: https://codereview.chromium.org/1924183003