panfrost: Add NIR-based sysval lowering pass

panfrost: Add NIR-based sysval lowering pass

Add a NIR pass to lower all the sysvals seen in the GL driver to load_ubo
intrinsics. These load_ubo intrinsics will be pushed to uniforms by the backend
compiler as usual. This will let us remove all sysval handling from the backend
compilers.

This is a direct NIR port of the existing pan_sysvals.c infrastructure and the
consumers in the Midgard/Bifrost compilers. It aims to be bug-for-bug compatible
to ease bisection.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20906>