anv: simplify push constant emissions

anv: simplify push constant emissions

Instead of allocating a push constant buffer per stage from the
dynamic state pool, we can use the same one for all stages.

We can do this because the push constant data is supposed to be
identical of all stages. Even if vkCmdPushConstants() allows to update
chunks of the push constant data differently per stage, this valid
usage guarantees that any chunk of push constant data used be 2
different stages must be identical :

   "For each byte in the range specified by offset and size and for
    each push constant range that overlaps that byte, stageFlags must
    include all stages in that push constant range’s
    VkPushConstantRange::stageFlags"

v2: Fix dirtying of stages (Jason)

v3: Move push constant data into base pipeline state struct (Jason)

v4: Remove duplicated field (Jason)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6183>