Remove support of SNMP GetBulk service

The SNMP protocol implemented in the lwIP component shall not support the service "GetBulk".

This is due to a potential security vulnerability:

OpenVAS scans the product for known vulnerabilities. During the OpenVAS scan on MCM controller with the filedbus EthernetIP, and scan results reported that
"By sending an SNMP GetBulk request of 41 bytes, we received a response of 960 bytes".

By sending high number of request could create Denial of Service. Successfully exploiting this vulnerability allows attackers to cause denial-of-service conditions against hosts.

Action Items:

• Statically switch off the support o "Getbulk" by calling LwIP_Snmp_SetGetBulkSupport(false) during SNMP initialization.
  The GetBulk service cannot be activated, neither by the host nor by a client in the network.
• Write a test case that ensures that the GetBulk service is not supported.
• Add migration note stating that the GetBulk service is not supported anymore.