Add QuicDispatcherPeer::GetTimeWaitListManager() method. This is so that redefining QuicDispatcherPeer could be avoided at https://github.com/envoyproxy/envoy/blob/master/test/extensions/quic_listeners/quiche/envoy_quic_dispatcher_test.cc#L41. Such a redefinition makes it impossible to use other QuicDispatcherPeer methods or to include test_tools/quic_dispatcher_peer.h at all from Envoy. gfe-relnote: n/a, test-only change. PiperOrigin-RevId: 278443582 Change-Id: I7fc3a19932e60b235929edb6d46b20e0bda4903b