turnip: refactor CmdDraw* functions (and a few fixes)

turnip: refactor CmdDraw* functions (and a few fixes)

This cleans up the CmdDraw* functions to be more straightforward. And a few
fixes applied while going through it:
* Fix indirect draw commands not adding the buffer->bo_offset, and ignoring
 drawCount/stride parameters (deqp tests not testing indirect draws very
 much apparently).
* Fixed a potential issue with RESTART_INDEX + secondary command bufs.
* Add missing logic for 8-bit indices

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
# Conflicts:
#	src/freedreno/vulkan/tu_cmd_buffer.c

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5579>