Remove our stream << overloads from non-test build targets.

Most are removed entirely, but RtcErrorType, RtpTransceiverDirection, IPAddress and
SocketAddress are kept behind gtest's #ifdef UNIT_TEST.

Bug: webrtc:8982
Change-Id: I36db19891e7d25aeacb08b9a08aa2b4004765e70
Reviewed-on: https://webrtc-review.googlesource.com/64143
Commit-Queue: Jonas Olsson <jonasolsson@webrtc.org>
Reviewed-by: Benjamin Wright <benwright@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22916}

api/rtcerror.cc

@@ -93,10 +93,6 @@ void RTCError::set_message(std::string&& message) {
   }
 }
 
-std::ostream& operator<<(std::ostream& stream, RTCErrorType error) {
-  return stream << ToString(error);
-}
-
 // TODO(jonasolsson): Change to use absl::string_view when it's available.
 std::string ToString(RTCErrorType error) {
   int index = static_cast<int>(error);