nir/builder: Add a name format arg to nir_builder_init_simple_shader().

nir/builder: Add a name format arg to nir_builder_init_simple_shader().

This cleans up a bunch of gross sprintfs and keeps the caller from needing
to remember to ralloc_strdup.  I added a couple of '"%s", name ? name :
""' to radv where I didn't fully trace through whether a non-null name was
being passed in.

I also took the liberty of adding a basic name to a few shaders (pan_blit,
unit tests)

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7323>