[YANG]: Fix SNMP_AGENT_ADDRESS_CONFIG yang model

[SuvarnaMeenakshi]

fixes #16011

Why I did it

1. seeing below warning ,essage:
   libyang[1]: Default value "" in the list key "port" is ignored. (/sonic-snmp:sonic-snmp/SNMP_AGENT_ADDRESS_CONFIG/SNMP_AGENT_ADDRESS_LIST)
   libyang[1]: Default value "" in the list key "vrf_name" is ignored. (/sonic-snmp:sonic-snmp/SNMP_AGENT_ADDRESS_CONFIG/SNMP_AGENT_ADDRESS_LIST)

2. name of list is not <model_name>_LIST.

Work item tracking

• Microsoft ADO 25646016:

How I did it

1. Remove default value provided to key in yang model to avoid seeing below error:
   libyang[1]: Default value "" in the list key "port" is ignored. (/sonic-snmp:sonic-snmp/SNMP_AGENT_ADDRESS_CONFIG/SNMP_AGENT_ADDRESS_LIST)
   libyang[1]: Default value "" in the list key "vrf_name" is ignored. (/sonic-snmp:sonic-snmp/SNMP_AGENT_ADDRESS_CONFIG/SNMP_AGENT_ADDRESS_LIST)

2. Modify the LIST name to have <model_name>_LIST as this was failing yang validation during unit-tests.

How to verify it

unit-tests passing.
Before fix

admin@vlab-01:~$ sudo sonic-package-manager list
libyang[1]: Default value "" in the list key "port" is ignored. (/sonic-snmp:sonic-snmp/SNMP_AGENT_ADDRESS_CONFIG/SNMP_AGENT_ADDRESS_LIST)
libyang[1]: Default value "" in the list key "vrf_name" is ignored. (/sonic-snmp:sonic-snmp/SNMP_AGENT_ADDRESS_CONFIG/SNMP_AGENT_ADDRESS_LIST)
Name            Repository                   Description                   Version    Status
--------------  ---------------------------  ----------------------------  ---------  ---------
database        docker-database              SONiC database package        1.0.0      Built-In
dhcp-relay      docker-dhcp-relay            N/A                           1.0.0      Installed
eventd          docker-eventd                SONiC eventd package          1.0.0      Built-In
fpm-frr         docker-fpm-frr               SONiC fpm-frr package         1.0.0      Built-In
gbsyncd         docker-gbsyncd-vs            SONiC gbsyncd package         1.0.0      Built-In
lldp            docker-lldp                  SONiC lldp package            1.0.0      Built-In
macsec          docker-macsec                N/A                           1.0.0      Installed
mgmt-framework  docker-sonic-mgmt-framework  SONiC mgmt-framework package  1.0.0      Built-In
mux             docker-mux                   SONiC mux package             1.0.0      Built-In
nat             docker-nat                   SONiC nat package             1.0.0      Built-In
pmon            docker-platform-monitor      SONiC pmon package            1.0.0      Built-In
radv            docker-router-advertiser     SONiC radv package            1.0.0      Built-In
sflow           docker-sflow                 SONiC sflow package           1.0.0      Built-In
snmp            docker-snmp                  SONiC snmp package            1.0.0      Built-In
swss            docker-orchagent             SONiC swss package            1.0.0      Built-In
syncd           docker-syncd-vs              SONiC syncd package           1.0.0      Built-In
teamd           docker-teamd                 SONiC teamd package           1.0.0      Built-In
telemetry       docker-sonic-telemetry       SONiC telemetry package       1.0.0      Built-In

After fix:

admin@vlab-01:~$ sudo sonic-package-manager list
Name            Repository                   Description                   Version    Status
--------------  ---------------------------  ----------------------------  ---------  ---------
database        docker-database              SONiC database package        1.0.0      Built-In
dhcp-relay      docker-dhcp-relay            N/A                           1.0.0      Installed
eventd          docker-eventd                SONiC eventd package          1.0.0      Built-In
fpm-frr         docker-fpm-frr               SONiC fpm-frr package         1.0.0      Built-In
gbsyncd         docker-gbsyncd-vs            SONiC gbsyncd package         1.0.0      Built-In
lldp            docker-lldp                  SONiC lldp package            1.0.0      Built-In
macsec          docker-macsec                N/A                           1.0.0      Installed
mgmt-framework  docker-sonic-mgmt-framework  SONiC mgmt-framework package  1.0.0      Built-In
mux             docker-mux                   SONiC mux package             1.0.0      Built-In
nat             docker-nat                   SONiC nat package             1.0.0      Built-In
pmon            docker-platform-monitor      SONiC pmon package            1.0.0      Built-In
radv            docker-router-advertiser     SONiC radv package            1.0.0      Built-In
sflow           docker-sflow                 SONiC sflow package           1.0.0      Built-In
snmp            docker-snmp                  SONiC snmp package            1.0.0      Built-In
swss            docker-orchagent             SONiC swss package            1.0.0      Built-In
syncd           docker-syncd-vs              SONiC syncd package           1.0.0      Built-In
teamd           docker-teamd                 SONiC teamd package           1.0.0      Built-In
telemetry       docker-sonic-telemetry       SONiC telemetry package       1.0.0      Built-In

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111
• 202205
• 202211
• 202305

Tested branch (Please provide the tested image version)

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)

[ganglyu]

LGTM

[SuvarnaMeenakshi]

@qiluo-msft @StormLiangMS can you help merge this PR

[StormLiangMS]

LGTM