gallium: Add util_image_to_sampler_view helper
This helper is useful to implement images. This implementation is based on the one in Panfrost and extended to handle all pipe_image_views (notably including tex2d_from_buf which did not exist when the panfrost version was written). It will be used in both Panfrost and Asahi.
Signed-off-by: Alyssa Rosenzweig alyssa@rosenzweig.io