[gRIBI-5.1] Get RPC.

[robshakir]

• Validate that installed entries are returned via Get.
  • With ACK mode as RIB_ACK
  • With ACK mode as RIB_AND_FIB_ACK
  • In default network instance
  • in non-default network instance
• Measure latency of Get RPC on specific table sizes (benchmark). [for NHGs, NHs and prefixes]
  • n=100
  • n=1000
• Ensure that routes that are not possible to install in the FIB are not returned via Get when ACK mode is FIB ACK.
• Ensure that metadata is returned via Get

Things to be tested in functional tests.

• Ensure that routes that are not injected via gRIBI are not returned via Get.