rewrite_layer_chains does not respect kwargs

[lgray]

This is only exposed in #558 since otherwise everything gets wrapped in a ArgsKwargsPackedFunction which only ever has args, once we stop doing that (because it is expensive when called many times) unless it is really needed then it becomes apparent that only args are forwarded inside rewrite_layer_chains.

[martindurant]

I suppose we should make a test showing this

[lgray]

Presently it is manifest in the post dask 2024.12.0 code, it simply does not ask for task.kwargs, nor does it pass new kwargs to the newly made task.
The pre-_task_spec code also doesn't seem to deal with kwargs in any way, but it didn't come up in local testing of #558 since I didn't downgrade and recheck, etc.

https://github.com/dask-contrib/dask-awkward/blob/main/src/dask_awkward/lib/optimize.py#L372-L384