anv: Split command buffer attachment setup in three

anv: Split command buffer attachment setup in three

This commit splits genX(cmd_buffer_setup_attachments)() into three
functions: one which sets up cmd_buffer->state.attachments, one which
allocates surface states, and one which fills out the surface states.
While we're here, we make both functions take the framebuffer (if any)
as an argument instead of pulling it from the command buffer so it's
more clear what things are inputs to the functions.  We also make the
render pass and framebuffer parameters const as those are immutable
objects.  The only functional change here should be that we now
vk_zalloc the attachments which should be a bit safer.

Reviewed-by: Rafael Antognolli <rafael.antognolli@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4393>