Deprecate/block packets with a missing/invalid hop_start value (pre-hop firmware) (related to issue #7369) (#9476)

* Deprecate forwarding for invalid hop_start

* Add pre-hop packet drop policy

* Log ignored rebroadcasts for pre-hop packets

* Respect pre-hop policy ALLOW in routing gates

* Exempt local packets from pre-hop drop policy

* Format pre-hop log line

* Add MODERN_ONLY rebroadcast mode for pre-hop packets

* Simplify implementation for drop packet only behaviour

* Revert formatting-only changes

* Match ReliableRouter EOF formatting

* Make pre-hop drop a build-time flag

* Rework to compile/build flag MESHTASTIC_PREHOP_DROP

* Set MESHTASTIC_PREHOP_DROP off by default

* Inline pre-hop hop_start validity check

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>
Co-authored-by: Jord <650645+DivineOmega@users.noreply.github.com>

src/mesh/Router.cpp

@@ -851,6 +851,12 @@ void Router::perhapsHandleReceived(meshtastic_MeshPacket *p)
         return;
     }
 
+    if (shouldDropPacketForPreHop(*p)) {
+        logHopStartDrop(*p, "pre-hop drop");
+        packetPool.release(p);
+        return;
+    }
+
     if (shouldFilterReceived(p)) {
         LOG_DEBUG("Incoming msg was filtered from 0x%x", p->from);
         packetPool.release(p);