Some initial testing with orjson indicates performance varies from
slightly better than pysqlite to about 2x slower depending on the type
of query.
Performance could be improved by building the Python list in rspy
instead of sending back json that needs to be decoded, but it may make
more sense to rewrite the hotspots in Rust instead. More testing is
required in any case.
- Adding files inside Anki now updates the media DB, so a full file
scan at sync time is no longer required if no other changes have been
made.
- Use a protobuf message for backend initialization, and return a
string error if initialization fails.
