Add support for zarr trace backend

[lucianopaz]

Following pymc-devs/pymc#7687 it would be great to have a zarr native storage backend for nutpie. The layout defined in pymc.backends.zarr.ZarrTrace is simple enough to copy and be used generically. pymc would then be able to simply load the trace from the underlying storage without much need to nutpie wrappers. From the rust side of things, it looks like this is the most up to date zarr rust package.