Add TabPFN explainer

[mmschlk]

We should add a TabPFNExplainer object that incorporates a remove-and-contextualize paradigm for model explanations. This is, I think, also described in [1].

References

[1] Rundel, D., Kobialka, J., von Crailsheim, C., Feurer, M., Nagler, T., Rügamer, D. (2024). Interpretable Machine Learning for TabPFN. In: Longo, L., Lapuschkin, S., Seifert, C. (eds) Explainable Artificial Intelligence. xAI 2024. Communications in Computer and Information Science, vol 2154. Springer, Cham. https://doi.org/10.1007/978-3-031-63797-1_23

[mmschlk]

Closed in #302.