Make embedded btc wallet produce less logs

[altafan]

There's no way to change the level of the logs a service produces. Rather, we can set the the min log level for it and make those of the levels above disappear.

This makes the embedded btc wallet produce fewer logs by setting the log level of all components to warning.

NOTE: There's no way to set a log level for the sqlite db we use currently modernc.org/sqlite. Maybe we should move to something else? Is there a specific reason we chose this one? @louisinger @tiero

Closes #287

Please @louisinger @tiero review

[tiero]

It's the only go native so no CGO

[tiero]

Something even lower than warn? Like debug or trace?

[altafan]

These are the levels. If we set Trace log level, it means we want to see the logs of all levels, if we use Debug we exclude only trace logs and so on. We use Warn to see only warning errors and criticals and exclude all the other levels.