refactor(policy): update policy.proto

proto/policy.proto

...y/src/main/java/eu/teraflow/policy/PolicyGatewayImpl.java

...olicy/src/main/java/eu/teraflow/policy/PolicyService.java

...y/src/main/java/eu/teraflow/policy/PolicyServiceImpl.java

...cy/src/main/java/eu/teraflow/policy/model/PolicyRule.java

...c/main/java/eu/teraflow/policy/model/PolicyRuleEvent.java

...rc/main/java/eu/teraflow/policy/model/PolicyRuleType.java

...y/src/test/java/eu/teraflow/policy/PolicyServiceTest.java

...enerated-sources/grpc/policy/MutinyPolicyServiceGrpc.java

src/policy/target/generated-sources/grpc/policy/Policy.java

...y/target/generated-sources/grpc/policy/PolicyService.java

...rget/generated-sources/grpc/policy/PolicyServiceBean.java

...et/generated-sources/grpc/policy/PolicyServiceClient.java

...rget/generated-sources/grpc/policy/PolicyServiceGrpc.java

src/policy/target/kubernetes/kubernetes.yml