[gRIBI-3.5] ACK types

[robshakir]

Compliance tests to cover:

• RIB_ACK received when requested by client.
• RIB_AND_FIB_ACK received when requested by client.
  • When entry can be resolved wholly in gRIBI.
• FIB_ACK not sent when system cannot resolve entry.
• FIB_ACK received successfully when resolution is recursive inside gRIBI.
  • 1-layer recursion
  • 2-layer recursion

To be implemented in functional tests:

• Successfully receive RIB_ACK when entry cannot be resolved within gRIBI.
• FIB_ACK received successfully when resolution is recursive outside of gRIBI.
• RIB_AND_FIB_ACK received when requested by client:
  • When entry relies on external RIB to resolve the entry.