tracee: refactor remove protocol.Event

`tracee-ebpf | tracee-rules` have a generic protocol in between for communication (protocol.Event). This should be removed once the unified binary (tracee) becomes the default solution, and we decide to drop `tracee-ebpf`, and `tracee-rules`.

With `signatures` as part of the pipeline, all the communication could be done with `trace.Event`instead of converting back and forth from [`tracee.Event -> protocol.Event`](https://github.com/aquasecurity/tracee/blob/main/pkg/ebpf/rule_engine.go#L47)