broadcom/compiler: call nir_opt_gcm with a custom strategy

broadcom/compiler: call nir_opt_gcm with a custom strategy

nir_opt_gcm get us worse shader-db stats, but that is expected. But we
want to prevent to get worse values on spill/fills. Analyzing the
outcome with shader-db, this mostly happen with shaders that are
already complex, and are already spilling/filling.

So the best option here is adding a new strategy, that fall backs if
we get spill/fill using nir_opt_gcm.

It is not clear in which order we should disable gcm. For now we
disable it before loop unrolling.

We get a slight performance gain (in average) using nir_opt_gcm.

We don't show the shaderdb stats, as they are worse, but as mentioned,
this is expected.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17185>