anv: bump internal descriptor index fields to 32bits

anv: bump internal descriptor index fields to 32bits

Prior to supporting VK_EXT_descriptor_indexing all of our descriptor
limits where below 64k which fitted a uint16_t. Now all of those can
go up to 2^20 entries so we need 32bits indexes to keep track of them.

This change leaves the dynamic indexes at 16bits. We could arguably
bump them too, up to the reviewer's taste.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: 6e230d7607f9b3 ("anv: Implement VK_EXT_descriptor_indexing")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/4636
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10228>