Fix JDBC type for DECIMAL columns; add test

[elefeint]

This PR allows DECIMAL(W,S) types to be interpreted as DECIMAL JDBC type. Currently the type is returned as a generic JAVA_OBJECT because DECIMAL(W,S) does not match DECIMAL` in the case statement. This is similar to 0.9.2 behavior except the start-of-string matching is done in SQL rather than Java.

I wonder if a better fix would be to use data_type_id from duckdb_columns() rather than data_type from information_schema.columns? It would require adding hardcoded duckdb type numbers into DuckDBColumnType. The test is useful either way.

There is a tiny unrelated improvement to Assertions utility, allowing the calling code to add a prefix to indicate which one of the loop iterations failed.

Fixes duckdb/duckdb#11365

[Mause]

Thanks!