Add Spring gRPC Server Health Check Support

[philwebb]

Add support for gPRC server health with features take from spring-grpc-server-spring-boot-autoconfigure.

The following differences are anticipated:

• Adapting the actuator endpoint doesn't feel like the best approach now that we have a health modules. It would be better to work directly with the health contributors.

Commits from Spring gRPC to consider:

• spring-projects/spring-grpc@15e5372