2.6 <- Next hop router (#6005)

* Initial version of NextHopRouter

* Set original hop limit in header flags

* Short-circuit to FloodingRouter for broadcasts

* If packet traveled 1 hop, set `relay_node` as `next_hop` for the original transmitter

* Set last byte to 0xFF if it ended at 0x00
As per an idea of @S5NC

* Also update next-hop based on received DM for us

* temp

* Add 1 retransmission for intermediate hops when using NextHopRouter

* Add next_hop and relayed_by in PacketHistory for setting next-hop and handle flooding fallback

* Update protos, store multiple relayers

* Remove next-hop update logic from NeighborInfoModule

* Fix retransmissions

* Improve ACKs for repeated packets and responses

* Stop retransmission even if there's not relay node

* Revert perhapsRebroadcast()

* Remove relayer if we cancel a transmission

* Better checking for fallback to flooding

* Fix newlines in traceroute print logs

* Stop retransmission for original packet

* Use relayID

* Also when want_ack is set, we should try to retransmit

* Fix cppcheck error

* Fix 'router' not in scope error

* Fix another cppcheck error

* Check for hop_limit and also update next hop when `hop_start == hop_limit` on ACK
Also check for broadcast in `getNextHop()`

* Formatting and correct NUM_RETRANSMISSIONS

* Update protos

* Start retransmissions in NextHopRouter if ReliableRouter didn't do it

* Handle repeated/fallback to flooding packets properly
First check if it's not still in the TxQueue

* Guard against clients setting `next_hop`/`relay_node`

* Don't cancel relay if we were the assigned next-hop

* Replies (e.g. tapback emoji) are also a valid confirmation of receipt

---------

Co-authored-by: GUVWAF <thijs@havinga.eu>
Co-authored-by: Thomas Göttgens <tgoettgens@gmail.com>
Co-authored-by: Tom Fifield <tom@tomfifield.net>
Co-authored-by: GUVWAF <78759985+GUVWAF@users.noreply.github.com>

src/mesh/NodeDB.h

@@ -116,6 +116,9 @@ class NodeDB
     /// @return our node number
     NodeNum getNodeNum() { return myNodeInfo.my_node_num; }
 
+    // @return last byte of a NodeNum, 0xFF if it ended at 0x00
+    uint8_t getLastByteOfNodeNum(NodeNum num) { return (uint8_t)((num & 0xFF) ? (num & 0xFF) : 0xFF); }
+
     /// if returns false, that means our node should send a DenyNodeNum response.  If true, we think the number is okay for use
     // bool handleWantNodeNum(NodeNum n);