define and implement packet API to disable and enable SNMP at runtime

A Profinet-generic packet API service shall be defined and implemented that allows Profinet (IO Device and IO Controller) applications to disable and enable SNMP at runtime.

If the service is used to disable SNMP, the IP stack shall get command to completely disable SNMP, thus requesting SNMP from port 161 shall be rejected with "port unreachable".

If the service is used to enable SNMP, the current Profinet stack SNMP configuration shall be applied. This is either the configuration set via record object CIMSNMPAdjust, or the default SNMP configuration as defined in Profinet specification.