add neigh-suppress CLI command

[iris00522]

What I did

add neigh-suppress CLI command

How I did it

reference evpn neigh-suppress HLD
https://github.com/Azure/SONiC/blob/master/doc/vxlan/EVPN/EVPN_VXLAN_HLD.md

5. ARP suppression
   - config neigh-suppress vlan <vlan-id>  <"on"/"off">
   - vlanid represents the vlan_id and on/off is enabled or disabled. By default ARP/ND suppression is disabled.

add neigh-suppress CLI command

How to verify it

root@as7726-32x-3:/home/admin#  config neigh-suppress vlan 1000
Usage: config neigh-suppress vlan [OPTIONS] <vid> <on|off>
Try "config neigh-suppress vlan -h" for help.

Error: Missing argument "<on|off>".  Choose from:
        on,
        off.
root@as7726-32x-3:/home/admin#  config neigh-suppress vlan 1000 on
Vlan1000 doesn't exist
root@as7726-32x-3:/home/admin#  config vlan add 1000
root@as7726-32x-3:/home/admin#  config neigh-suppress vlan 1000 on
root@as7726-32x-3:/home/admin#  config neigh-suppress vlan 1000 off
root@as7726-32x-3:/home/admin#  config neigh-suppress vlan 1000 on
root@as7726-32x-3:/home/admin# redis-cli
127.0.0.1:6379> select 4
OK
127.0.0.1:6379[4]> keys *SUPPRESS_VLAN_NEIGH*
1) "SUPPRESS_VLAN_NEIGH|Vlan1000"
127.0.0.1:6379[4]> HGETALL "SUPPRESS_VLAN_NEIGH|Vlan1000"
1) "suppress"
2) "on"
127.0.0.1:6379[4]>

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)

[lgtm-com]

This pull request introduces 1 alert when merging 119aaeacf3af4fbfe1edb6bc85338c2a2eaf1343 into 96143ee - view on LGTM.com

new alerts:

• 1 for Unnecessary pass

[iris00522]

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[mssonicbld]

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