ir3: Pass reserved_user_consts to ir3_shader_from_nir()

ir3: Pass reserved_user_consts to ir3_shader_from_nir()

ir3_shader_from_nir() calls ir3_optimize_nir(), which currently sets up
the const state. However, we need to know the number of user consts
reserved by the driver before setting up the const state, which means
that this information needs to be passed into ir3_shader_from_nir()
somehow rather than being set in the shader.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5500>