radv: update entrypoints generation from ANV

radv: update entrypoints generation from ANV

It's a massive rework loosely based on ANV. This introduces separate
dispatch tables for the instance, physical device and device objects.

This will help for implementing internal driver layers for SQTT.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3930>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3930>