Near-RT RIC Cherry integration tests

(1) Testing RIC-95 is essentially the implementation of “RIC On-Demand Health-Check” in https://lf-o-ran-sc.atlassian.net/wiki/pages/viewpage.action?pageId=12517420 However the implementation is different form the sequence diagram in that we have an “O1” REST interface to send a health check message to all or a selected list of E2 nodes and the we see “receive timestamps” that indicate that the message was received. The flow would include a near-RT RIC and an E2 node. The E2 node must implement the E2AP RIC Service Update procedure (no matter if it includes actual RAN function lists or not).

(2) This one does not correspond to any use case defined from RSAC. However, it's a sensible operability use case. Testing E2T statistics being sent to ONAP. With this patch (https://gerrit.o-ran-sc.org/r/c/ric-plt/vespamgr/+/5091) that has been added into vespamgr it should now be possible to get E2 stats (on number of packets over E2) via the path E2T->Prometheus->VESPA→(ONAP). The patch adds a environment variable VESMGR_PLT_CFG_FILE which contains the VESPA mapping for this path: Prometheus->VESPA. This part should already work: E2T→Prometheus. The case could also be expanded to actually add a E2 node (CU/DU) to actually see how statistics change as there is actual E2 communication with the near-RT RIC.