turnip: Define structs for transform feedback

turnip: Define structs for transform feedback

Define new structures for streamout buffers and state.
Most members of the state struct are taken from freedreno driver.

v2. Use IR3_MAX_SO_* and avoid using magic values.

v3. Remove the state of stream-output in tu_cmd_state and use one in
tu_pipeline and split out reset and enabled fields.

Signed-off-by: Hyunjun Ko <zzoon@igalia.com>
Reviewed-by: Jonathan Marek <jonathan@marek.ca>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3942>