Grpc-go: Add helper functions to chain server interceptors

[fho]

PR https://github.com/grpc/grpc-go/pull/2696 added helpers to chain client interceptors.
No analogous helper for server interceptors exist. To chain server interceptor the helpers from go-grpc-middleware or own helpers needs to be used.

To have a consistent API go-grpc should also provide helpers to chain server interceptors.

[dfawley]

@fho, this is reasonable, but the team does not currently have time to work on this. If you interested in sending a PR, we can review it and merge it.

[tukeJonny]

I want to try this issue.

[fho]

thank you @tukeJonny :-)