anv: Move shader hashing to anv_pipeline

anv: Move shader hashing to anv_pipeline

Shader hashing is very closely related to shader compilation.  Putting
them right next to each other in anv_pipeline makes it easier to verify
that we're actually hashing everything we need to be hashing.  The only
real change (other than the order of hashing) is that we now hash in the
shader stage.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>