Cancel response buffer copies if the client disconnects.

The response body does not throw exceptions if the client disconnects. It does that to avoid noisy logs for things that weren't the server's fault. However, that means that if the app is doing something that it wants to stop early then it needs to monitor the RequestAborted token.

Example: There's no need to copy this buffer to the response if the client has disconnected. Pass RequestAborted and catch OperationCancelledException for all usages of DrainBufferAsync.
https://github.com/dotnet/aspnetcore/blob/ef1f48ab97174131f1753efe9241295b1309d3e2/src/Mvc/Mvc.ViewFeatures/src/ViewComponentResultExecutor.cs#L158