* [Important] Namespace represents a subnet, such as kubernetes namespace, or 172.10.*.*. Make namespace concept as a part of service naming format.
* [Important] Add cluster concept, also as a part of service naming format. The cluster name would be
1. Add as {@link #SERVICE_NAME} suffix.
2. Add as exit span's peer, ${CLUSTER} / original peer
3. Cross Process Propagation Header's value addressUsedAtClient[index=8] (Target address of this request used on the client end).
* [Breaking Change] Remove deprecated `agent.instance_properties` configuration.
Recommend `agent.instance_properties_json`.
* The namespace and cluster would be reported as instance properties, keys are `namespace` and `cluster`. Notice, if
instance_properties_json includes these two keys, they would be overrided by the agent core.
* [Breaking Change] Remove the namespace from `cross process propagation` key.
b3ab1aed81