Remove closures from CancellationTokenExtensions.cs
Remove closures some send invocations.
- Removed from ServerSentEventsTransport and ForeverFrameTransport,
  and TransportDisconnectBase.
Remove closures from PersistentResponse.
Remove the closure in DisposableAction.
Remove delegate allocations from ForeverFrameTransport.
Fix delegate allocations in ServerSentEventsTransport.
Remove delegate allocations from TransportDisconnectBase.
Remove delegate allocations in TransportHeartBeat.
Fixed delegate definition
Removed some delegate allocations from WebSocketTransport.
Initial work removing delegate allocations from ForeverTransport.