Add config option for the grafana-agent log level

[marcusboden]

Enhancement Proposal

There are some issues that cause the grafana-agent itself to do some excessive logging (e.g. this issue. These are not (necessarily) bugs in the charm, but the since the charm doesn't allow me to configure the log level, I can't work around them easily.
I would like to have a config option for the charm that configures the log_level of the grafana-agent itself.