Plugins timeline should be observable

[ilya-siluyanov]

The problem: I see in the output when a plugin runs, but I don't see its runs duration

The solution: Create a log for events.
They can be 'plugin started', 'plugin finished', 'plugin prints a line', etc.
Based on an event type, we can assign handlers for them:

start -> [log_to_output, update_monitoring_state]
log -> [log_to_output]

As the first iteration, I see enough to create an entity which responsibilities are:

• read a paws config, create a gauge {plugin_name}_state
• when a metric changes, push current state to a prometheus pushgateway