anv/entrypoints: Only generate entrypoints for supported features

anv/entrypoints: Only generate entrypoints for supported features

This changes the way anv_entrypoints_gen.py works from generating a
table containing every single entrypoint in the XML to just the ones
that we actually need.  There's no reason for us to burn entrypoint
table space on a bunch of NV extensions we never plan to implement.

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