radv: Add support for per-primitive mesh shader outputs.

radv: Add support for per-primitive mesh shader outputs.

Generic per-primitive outputs:

They work similarly to other NGG outputs.
In the ISA they are param export instructions that are executed
on the primitive threads. These per-primitive params must be
sorted last among both mesh shader outputs and pixel shader inputs.

PS can read these inputs using the same old VINTRP instructions.
They use the same amount of LDS space as per-vertex PS inputs.

Special per-primitive outputs:

The VRS rate x, y, viewport and layer are special per-primitive
outputs which must go to the second channel of the primitive
export instruction, which is enabled by EN_PRIM_PAYLOAD.

If the PS wants to read these, they must also be exported as
a generic param.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13580>