fix(postgres): support uuid.to_pyarrow()

[NickCrews]

Partially addresses https://github.com/ibis-project/ibis/issues/8532. It just implements materializing uuids to pyarrow strings on the few backends where this is broken. Longer term, we might want to switch to materiliazing as pyarrow uuid types.

Based off of https://github.com/ibis-project/ibis/compare/main...double-thinker:ibis:fix/pyarrowtypes, but with the conversion stuff rebased on main, and relegated to the pyarrow.py file