UpdateCoreData.updateAnyPacketFrom: mirror firmware's lastHeard/snr/rssi/hopsAway update logic from NodeDB::updateFrom

[compumike]

While thinking about #1488 I realized that the logic for updating lastHeard was different from that used in the firmware.

In the firmware, updates to last_heard, rx_snr, rx_time, via_mqtt, hops_away are all set in one small function NodeDB::updateFrom, which receives all packets:

https://github.com/meshtastic/firmware/blob/28f53d132aa0d3903482ea9b475527068389244a/src/mesh/NodeDB.cpp#L1733-L1762

I think it simplifies things to use essentially the same logic in the client, especially since we update lastHeard etc from the radio whenever we connect and re-fetch the node database.

This change:

• 🐞 fixes a bug that lastHeard was being updated whenever we sent a DM, due to addContactFromURL calling upsertNodeInfoPacket with a synthetic packet
• deals with the position packets more consistently (only using rxTime to update lastHeard like the firmware does, and never position.timestamp which can be in the future)
• makes it so messages/ACKs/traceroutes/telemetry (for example) also update lastHeard and rxSnr etc
• factors out some common code
• and generally synchronizes this logic with the firmware.

I've tested it on iOS and macOS clients. The result seems to be a more active node list, no nodes with times in the future, and immediate updates to SNR/RSSI when viewing nearby nodes!

Checklist

• My code adheres to the project's coding and style guidelines.
• I have conducted a self-review of my code.
• I have commented my code, particularly in complex areas.
• I have verified whether these changes require an update to existing documentation or if new documentation is needed, and created an issue in the docs repo if applicable.
• I have tested the change to ensure that it works as intended.