Update `Machine.network_services` when new information is obtained

[shreyamalviya]

While testing #2999, @ilija-lazoroski found that "Scanned Servers" in the report shows "unknown" (should've been SSH).

This is because the UI shows Machine.network_services and that field is only updated once in ScanEventHandler when a TCPScanEvent is published. The network service is hard-coded to be updated to NetworkService.UNKNOWN.

A Machine's network_services should be updated every time we get new information about them (which is only from fingerprinting, as of now).

Tasks

Agent

• Change DiscoveredService.port from a NetworkPort to a SocketAddress and rename it (0d) @mssalvatore
• Create a FingerprintEvent model for fingerprinters to publish (0d) @mssalvatore
• Pass an IEventPublisher to the fingerprinters when we construct them (0d) @mssalvatore
• Update the fingerprinters to publish FingerprintEvents
  • HTTP (0d) @mssalvatore
  • MSSQL (0d) @shreyamalviya
  • SMB (0d) @shreyamalviya
  • SSH (0d) @shreyamalviya
• Modify the HTTPFingerprinter to publish HTTPRequestEvents (0d) @mssalvatore

Island

• Add an agent event handler to handle FingerprintEvents and update the machine (see ScanEventHandler for inspiration) (0.25d) - @shreyamalviya
  • See setup_agent_event_handlers()
• Refactor/rename ScanEventHandler._get_network_services_from_event() so that known network services are not overwritten (0d) @mssalvatore