Drop send_raw parameter threading: arp/icmp/igmp/ipv4 call net_send_raw directly

firmware/include/arp.h

@@ -1,5 +1,4 @@
 #pragma once
-#include <functional>
 #include <span>
 #include "eth.h"
 #include "ipv4.h"
@@ -21,7 +20,6 @@ struct __attribute__((packed)) header {
 static_assert(sizeof(header) == 28);
 
 void handle(std::span<const uint8_t> frame, span_writer& tx,
-            eth::mac_addr our_mac, ipv4::ip4_addr our_ip,
-            std::function<void(std::span<const uint8_t>)> send_raw);
+            eth::mac_addr our_mac, ipv4::ip4_addr our_ip);
 
 } // namespace arp