[action] [PR:17045] [SNMP]: Modify minigraph parser to update SNMP_AGENT_ADDRESS_CONFIG table (#17045)

[mssonicbld]

Why I did it

SNMP query over IPv6 does not work due to issue in net-snmp where IPv6 query does not work on multi-nic environment.
To get around this, if snmpd listens on specific ipv4 or ipv6 address, then the issue is not seen.
We plan to configure Management IP and Loopback IP configured in minigraph.xml as SNMP_AGENT_ADDRESS in config_db., based on changes discussed in sonic-net/SONiC#1457.

Work item tracking

• Microsoft ADO (number only):26091228

How I did it

Modify minigraph parser to update SNMP_AGENT_ADDRESS_CONFIG with management and Loopback0 IP addresses.
Modify snmpd.conf.j2 to use SNMP_AGENT_ADDRESS_CONFIG table if it is present in config_db, if not listen on any IP.
Main change:

1. if minigraph.xml is used to configure the device, then snmpd will listen on mgmt and loopback IP addresses,
2. if config_db is used to configure the device, snmpd will listen IP present in SNMP_AGENT_ADDRESS_CONFIG if that table is present, if table is not present snmpd will listen on any IP.

How to verify it

config_db.json created from minigraph.xml for single asic VS image with mgmt and Loopback IP addresses.

    "SNMP_AGENT_ADDRESS_CONFIG": {
        "10.1.0.32|161|": {},
        "10.250.0.101|161|": {},
        "FC00:1::32|161|": {},
        "fec0::ffff:afa:1|161|": {}
    },
 .....
 
 snmpd listening on the above IP addresses:
 admin@vlab-01:~$ sudo netstat -tulnp | grep 161
tcp        0      0 127.0.0.1:3161          0.0.0.0:*               LISTEN      71522/snmpd         
udp        0      0 10.250.0.101:161        0.0.0.0:*                           71522/snmpd         
udp        0      0 10.1.0.32:161           0.0.0.0:*                           71522/snmpd         
udp6       0      0 fec0::ffff:afa:1:161    :::*                                71522/snmpd         
udp6       0      0 fc00:1::32:161          :::*                                71522/snmpd  

[mssonicbld]

Original PR: #17045