Missing `Http2ServerResponse.setHeaders()`

### What is the problem this feature will solve? Make it possible to use `response.setHeaders()` on both old HTTP response objects and ones coming from `node:http2`. BTW I wasn't sure if this should be a "feature request" or a "bug." ### What is the feature you are proposing to solve the problem? Add the method `http2.Http2ServerResponse.setHeaders()` to have the same API as `http.OutgoingMessage.setHeaders()`. See <https://nodejs.org/api/http.html#outgoingmessagesetheadersheaders>. ### What alternatives have you considered? * Avoiding using `setHeaders()` at all. * Monkey-patching `Http2ServerResponse`. * Just writing two versions of my own set-headers code, on the assumption that, when available, `setHeaders()` is the most efficient option.