fix: fdb tables multiple IPs and IPs from other devices adding extra rows (#6930)

Fix missing IPs because the ARP entries are on different port_id
Update arp discovery to use snmpwalk_group() additional fix in that function
Fix removal of arp entries
Fix a debug output type in fdb discovery

sql-schema/199.sql

@@ -0,0 +1 @@
+ALTER TABLE `ipv4_mac` ADD `device_id` INT NULL AFTER `port_id`;