pulsar monitor --all generates loop of events

[MatteoNardi]

#122 introduced the possibility to monitor pulsar events from the cli client pulsar-exec pulsar. The issue is that unless the pulsar-exec binary is added to the process filtering whitelist, running pulsar monitor --all will trigger a loop of events, making the whole output very hard to understand:

• Traffic between pulsard and pulsar happens over a unix socket, using a websocket
• This will make network-monitor generate Receive events for pulsar
• These events will be sent over the websocket
• This will generate more traffic, which in turn will generate more events, creating a loop

For a similar reason, we ignore all events coming from the same PID as the running pulsard executable:
https://github.com/Exein-io/pulsar/blob/cf8469e47e0fa6714853291fbb38574517ac7d33/modules/process-monitor/src/filtering/initializer.rs#L166-L172

While the cleanest solution would be to add pulsar-exec to the configuration process-monitor.whitelist_children, this would be easy to forget. We'd like to improve the default behavior, so we've decided to:

• Automatically add the current process executable path to the whitelist_children (this works because pulsard and pulsar share the same executable, pulsar-exec)
• Add an option to optionally disable this behavior