nir: Add clone/hash/serialize support for non-uniform tex instructions.

These were missed when the fields got added. Added it everywhere where
texture_index got used and it made sense.

Found this in "The Surge 2", where the inliner does not copy the fields,
resulting in corruption and hangs.

Fixes: 3bd54576 "nir: Add a lowering pass for non-uniform resource access"
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/1203


Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3246>
(cherry picked from commit 69bdc1c5)