anv: Pre-compute push ranges for graphics pipelines

anv: Pre-compute push ranges for graphics pipelines

It turns off that emitting push constants is one of the hottest paths in
the driver and ANY work we do there costs us.  By pre-computing things a
bit ahead of time, we shave 5% off the runtime of a CPU-limited example
running with the Dawn WebGPU implementation.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>