Python log storage

[evertlammerts]

Fixes #480

This adds a PythonLogStorage that logs to both a logging.Logger named "duckdb" and to the in-memory storage. The storage is enabled by default.

Example:

import logging, duckdb

logging.basicConfig(level=logging.DEBUG)

con = duckdb.connect()
con.execute("SELECT list_transform([1,2,3], x -> x+1)")

Outputs:

WARNING:duckdb:Deprecated lambda arrow (->) detected. Please transition to the new lambda syntax, i.e.., lambda x, i: x + i, before DuckDB's next release.
Use SET lambda_syntax='ENABLE_SINGLE_ARROW' to revert to the deprecated behavior.
For more information, see https://duckdb.org/docs/stable/sql/functions/lambda.html.

And SELECT message FROM duckdb_logs still works as well.