New PCEP CLI changes for 20.3 release

- Introduced the concept of a pcep-config-group,
  which currently can be used as a common configuration
  for PCEs, but will later allow PCCs to be configured
  when/if pathd is a PCE.
- PCEs are now configured as a root node using the
  pcc-peer configuration. The pcc-peer can be configured
  and modified before being referenced by the PCC, thus
  allowing for modifications without reconnects.
- The framework for Multi-PCE is in place, and will be
  finished in subsequent patches.

lib/command.h

@@ -147,7 +147,9 @@ enum node_type {
 	PW_NODE,		 /* Pseudowire config node */
 	SEGMENT_LIST_NODE,	 /* SR segment list config node */
 	SR_POLICY_NODE,		 /* SR policy config node */
-	PCC_NODE,                /* PCC config node */
+	PCEP_CONFIG_GROUP_NODE,	 /* PCEP peer Configuration Group node */
+	PCC_PEER_NODE,		 /* PCC Peer (PCE) config node */
+	PCC_NODE,		 /* PCC config node */
 	VTY_NODE,		 /* Vty node. */
 	FPM_NODE,		 /* Dataplane FPM node. */
 	LINK_PARAMS_NODE,	/* Link-parameters node */