radv: introduce the concept of meta save flags

radv: introduce the concept of meta save flags

This will allow us to save/restore the different states on-demand
based on the meta operation. For now, this saves/restores all
states. Compute will follow once the graphics part is done.

The main idea is to merge all save/restore helpers.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>