TransportChannel#sendResponse has inconsistent release behaviour #78533
Description
TcpTransportChannel#sendResponse ends up calling TransportResponse#decRef once the response is sent, but the other implementations (notably DirectResponseChannel#sendResponse) do not. I don't have evidence that this is observable as a bug today but I expect it will bite us at some point in the future.
I'd rather we didn't have methods that implicitly called decRef like that, it's so much trappier than having every incRef/decRef pair explicitly co-located, so I'd prefer to add an on-sent listener argument to TransportChannel#sendResponse.
Relates #76474