Add new ROUTER_LATE role (#5528)

Will always rebroadcast packets, but will do so after all other modes.
Intended for router nodes that are there to provide additional coverage
in areas not already covered by other routers, or to bridge around
problematic terrain, but should not be given priority over other routers
in order to avoid unnecessaraily consuming hops.

By default, this role will rebroadcast during the normal client window.
However, if another node is overheard rebroadcasting the packet, then it
will be moved to a second window *after* the normal client one, with the
same timing behaviour.

src/mesh/RadioInterface.h

@@ -173,9 +173,18 @@ class RadioInterface
     /** The delay to use when we want to send something */
     uint32_t getTxDelayMsec();
 
+    /** The CW to use when calculating SNR_based delays */
+    uint8_t getCWsize(float snr);
+
+    /** The worst-case SNR_based packet delay */
+    uint32_t getTxDelayMsecWeightedWorst(float snr);
+
     /** The delay to use when we want to flood a message. Use a weighted scale based on SNR */
     uint32_t getTxDelayMsecWeighted(float snr);
 
+    /** If the packet is not already in the late rebroadcast window, move it there */
+    virtual void clampToLateRebroadcastWindow(NodeNum from, PacketId id) { return; }
+
     /**
      * Calculate airtime per
      * https://www.rs-online.com/designspark/rel-assets/ds-assets/uploads/knowledge-items/application-notes-for-the-internet-of-things/LoRa%20Design%20Guide.pdf