Change STOP_SENDING frame related APIs to use QuicRstStreamError type.

Change QuicControlFrameManager::WriteOrBufferStopSending(),
QuicSession::SendStopSending(), QuicStream::OnStopSending(), and
QuicStopSendingFrame constructor to take QuicRstStreamError arguments.
Add QuicStopSendingFrame::error_code member.  Remove
QuicStopSendingFrame::application_error_code and QuicApplicationErrorCode.

Previously the error code was stored in an uint16_t, now in a
QuicRstStreamError, which has a wider underlying type of int.  However, the
truncation logic for incoming STOP_SENDING frames in
QuicFramer::ProcessStopSendingFrame() is unchanged.
PiperOrigin-RevId: 329762228
Change-Id: Iab016a992e9bdde945ed96c7ba03b86276c1e968
diff --git a/quic/core/quic_control_frame_manager.h b/quic/core/quic_control_frame_manager.h
index 7615754..d57d120 100644
--- a/quic/core/quic_control_frame_manager.h
+++ b/quic/core/quic_control_frame_manager.h
@@ -77,7 +77,8 @@
 
   // Tries to send an IETF-QUIC STOP_SENDING frame. The frame is buffered if it
   // can not be sent immediately.
-  void WriteOrBufferStopSending(uint16_t code, QuicStreamId stream_id);
+  void WriteOrBufferStopSending(QuicRstStreamErrorCode code,
+                                QuicStreamId stream_id);
 
   // Tries to send an HANDSHAKE_DONE frame. The frame is buffered if it can not
   // be sent immediately.