Make log level configurable

[gudvinr]

Is your feature request related to a problem? Please describe.
jellyfin mpv shim is spamming in logs, which is especially noticeable when you launch it as daemon. That way, when you use journalctl, you get spammed by ping messages.

Right now, logging is hardcoded in log_utils.py by setting level for root_logger to DEBUG.

Describe the solution you'd like

There is mpv_log_level parameter already. Instead, log_level could be introduced, which can be applied to both mpv and shim itself. mpv_log_level can be either dropped or left to be used as additional parameter to override log levels for mpv.

Describe alternatives you've considered

• Patching code myself
• Writing logs to file (which are still verbose and take up space)