bug: events aggregator is not implemented

[anjmao]

Aggregator code here looks incorrect https://github.com/cilium/tetragon/blob/main/pkg/aggregator/aggregator.go#L33

• If aggregation options are passed it doesn't aggregate in time windows but just writes to GetEventChannel() and immediately sends event to channel received.
• flush() only clears cache map, but there are no writes to it.
• Looks like the idea was to use simple map cache map[string]*tetragon.GetEventsResponse, but not sure about that. Normally aggregations would keep numerical correctness which is a lot more complex to implement.

[kkourt]

Thanks!

Would it be possible to write a unit test that exposes the issue?