Add code to K8s plugin to create a REGISTER module.

REGISTER module in k8s plugin code. Other multicloud plugins support register API for cloud registration by AAI/ESR (ESR Is EOL) and currently manual hacks and workarounds are done for k8s instantiation.

 Example Flow of REGISTER module:

      REGISTER receives a call from CLI at http://MSB_IP:MSB_PORT/api/multicloud-k8s/v2/registry (should match other multicloud plugin API)

1. REGISTER gets node feature labels from HPA Placement Plugin using GetFeaturesPerNode_()_ a method of HPA Placement Plugin.
   1. See https://gerrit.onap.org/r/c/multicloud/k8s/+/97716/1/src/k8splugin/plugins/adapters/hpa/hpa_plugin.go#66 
   2. GetFeaturesPerNode() requires a cluster-name and returns a map[<node-name>]<string of features on node>
   3. Node name should be used as the flavor name, whereas each feature should be a "--property <key=value>" in the flavor
2. REGISTER converts Node Feature Labels to compute flavors consumable by AAI per node
   1. I.E. each node is a flavor with all node capabilities in that node contained in the flavor
3. REGISTER creates update cloud/tenant flavors in AAI (can this use AAI K8s Module being created here: https://gerrit.onap.org/r/c/multicloud/k8s/+/96063 Tech mahendra has agreed to make it more generic)
4. K8s AAI micro service pushes compute cloud/tenant and flavor info to AAI. (Otherwise code needs to be created to push this info to AAI)