The duckdb.reset_ddb() function should remove all temporary DuckDB tables

[JelteF]

In #281 the function duckdb.reset_ddb() was added, which recreates the in memory database. This has as a sideeffect that all temporary duckdb tables are lost. We should also remove the matching Postgres tables from the catalog in that case.

This is definitely not a critical bug. The duckdb.reset_ddb() function is mostly meant for debugging at this point. But I at least thought we should track that this is an issue. Especially since it's probably not too hard to fix.