[Enh]: Improve support for Decimal dtype

Polars [Decimal dtype](https://docs.pola.rs/api/python/dev/reference/api/polars.datatypes.Decimal.html) support is no longer unstable (as of polars 1.35.0, https://github.com/pola-rs/polars/pull/25020).

It might be time for us to have better support for it as well