Add Service Directory integration

**Is your feature request related to a problem? Please describe.**
Service Directory was GA on Feb 16th, read more [here](https://cloud.google.com/blog/products/networking/service-directory-is-ga-and-adds-automatic-service-registration). It would be great to add an integration.

**Describe the solution you'd like**
Register a service when it become healthy using `spring.application.name` as an alias. Also, interaction between services using the alias registered in the Service Directory.