Implement proper ORM benchmarking; fix profiler

 - torsearch/benchmark.py is now used test out how the ORM performs on
different machines and/or database setups. times and EXPLAINs are
logged.

 - query_info can now also output EXPLAIN (BUFFERS, ANALYZE)

 - fixed small issues in profiler

 - onionoo_api uses from_statement.

we can now compare queries run from from_statement, and using
sqlalchemy primitives (select(), etc.) in theory, if we do it properly,
there shouldn't be a difference.