anv: split pipeline programming into instructions

anv: split pipeline programming into instructions

The goal of this change it to move away from a single batch buffer
containing all kind of pipeline instructions to a list of instructions
we can emit separately.

We will later implement pipeline diffing and finer state tracking that
will allow fewer instructions to be emitted.

This changes the following things :

   * instead of having a batch & partially packed instructions, move
     everything into the batch

   * add a set of pointer in the batch that allows us to point to each
     instruction (almost... we group some like URB instructions,
     etc...).

At pipeline emission time, we just go through all of those pointers
and emit the instruction into the batch. No additional packing is
involved.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24536>