Update dependencies and improve pyo3

[heftig]

• Update all dependencies so that cargo outdated -R is satisfied.

• Use declarative pyo3 modules.

• The docs and the code disagreed on whether the auto compressor entry point is named compress_largest_rooms, compress_state_events_table or compress_chunks_of_database.

  Rename the entry point to run_compression, matching the manual compressor, and fix the docs. Leave compress_largest_rooms as another entry point to avoid breaking existing code.

• Provide a default for default_levels.

• Use &str instead of String in Python signatures where it simplifies the code or is necessary to include the default in the text signature.

• Release the GIL while running the manual compressor.

• Use map_err to simplify error conversion a bit.