Large number of arg_id_to_{dtype,descr} deprecation warnings raised internally by loopy

[connorjward]

We are seeing a large number of

/usr/lib/python3.12/dataclasses.py:1581: DeprecationWarning: arg_id_to_dtype passed to InKernelCallable was not hashable. This usage is deprecated and will stop working in 2026.

and

/usr/lib/python3.12/dataclasses.py:1581: DeprecationWarning: arg_id_to_descr passed to InKernelCallable was not hashable. This usage is deprecated and will stop working in 2026.

warnings getting thrown in our CI (example).

(firedrakeproject/firedrake#3992)

I have tracked this down to find that this is getting throw internally inside of loopy where you have lines such as:

            return (
                    self.copy(name_in_target=name,
                        arg_id_to_dtype={
                            0: NumpyType(dtype),
                            -1: NumpyType(result_dtype)}),
                    callables_table)

where I expect arg_id_to_dtype should be an immutabledict.

[alexfikl]

I have at least some of these fixed from a similar avalanche of warnings in https://github.com/inducer/pytential. I'll go ahead and clean it up and post a PR. 😁