feat (draw_ext): add render encoder to draw callbacks

[nreagan]

Not sure how you'll feel about adding the render encoder to the callback, but it's needed to bind the shader

EDIT did realize that I don't like that it assumes the shader will be set........really needs a way to tell if the shader has been set or not.

[nreagan]

Not sure how you'll feel about adding the render encoder to the callback, but it's needed to bind the shader

EDIT did realize that I don't like that it assumes the shader will be set........really needs a way to tell if the shader has been set or not.

I'm thinking now that having a separate callback for setting the shader may be simplest.