Currently, public services that publish their onion addresses have a
`requires` dependeny on service `onion-addresses`, so they are restarted
when `onion-addresses` restarts.
This has the downside that most of nix-bitcoin's services are restarted
when a new onion service is added and the system config has the following common settings:
- nix-bitcoin.onionServices.bitcoind.public = true
- nix-bitcoin.operator.enable = true
Sequence of events:
1. onion service is added
2. `onion-addresses` restarts, because the new onion service is made available to `operator`
3. bitcoind restarts
4. all depending services restart
Fix this by using a `wants` dependency.
a3490dfc0f