should support balancing many onion addresses

Currently for v3 onion services, onionbalance only can balance a single hostname. As a result, both tor and debian need to run 40-60 onionbalance instances each. That is not cheap on memory use. For instance, a VM with only 6 gigabytes of ram is not able to provide the onionbalance service for debian.

Please make onionbalance be able to balance any number of v3 services.

On top, it'd be nice if it could balance both v3 and v2 at the same time. But that's less of an issue.