panfrost: Prepack fragment properties/preload

panfrost: Prepack fragment properties/preload

This isn't as clean as vertex shaders, since some of this state is only
known at draw-time (e.g. some reasons we might disable early-Z). But we
can still pack as much as we can ahead-of-time and then OR together
what's left at draw-time.

Thank you to Kristian for this one crazy trick (blob developers hate
it! er...)

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6440>