Implement Multiple services per one endpoint and generic sidecar in 4G example

[electrocucaracha]

This PR provides support to multiple services in one endpoint, this change opens the possibility to create a generic sidecar which address most of the scenarios providing the NSE information through K8s annotations. Using a generic sidecar can help to improve the NSM adoption, reduce the number of sidecar implementations, focus on business logic, etc.

This implementation correspond to this proposal.