[Journald] Implement status reporting for Elastic-Agent

[belimawr]

The journald input should report input status directly to Elastic-Agent. That can be done by implementing the following interfaces:

beats/libbeat/management/status/status.go

Lines 46 to 55 in b7f9f1f

	type StatusReporter interface {
	// UpdateStatus updates the status of the unit.
	UpdateStatus(status Status, msg string)
	}
	// WithStatusReporter provides a method to set a status reporter
	type WithStatusReporter interface {
	// SetStatusReporter sets the status reporter
	SetStatusReporter(reporter StatusReporter)
	}