intel/isl: Pull the uncompressed surface view code from anv

This adds a helper isl_surf_get_uncompressed_surf for creating a surface which provides an uncompressed view into a compressed surface. The code is basically a direct port of the uncompressed surface code from the Vulkan driver which, in turn, was a port from BLORP. It also improves the code somewhat and then ports iris to use it instead of hand-rolling it yet again.