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

This is a reland of c841d18d257ba8e4ed7d77d105e3c46006bb1e7e

Original change's description:
> 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}

TBR=deadbeef@webrtc.org,kwiberg@webrtc.org,asapersson@webrtc.org,jonasolsson@webrtc.org,benwright@webrtc.org

Bug: webrtc:8982
Change-Id: Ibe08c6270e5e693eb661a6ce9e8f074b34ef8123
Reviewed-on: https://webrtc-review.googlesource.com/71161
Commit-Queue: Jonas Olsson <jonasolsson@webrtc.org>
Reviewed-by: Jonas Olsson <jonasolsson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22949}
diff --git a/api/rtcerror.h b/api/rtcerror.h
index d7dec29..c87ce91 100644
--- a/api/rtcerror.h
+++ b/api/rtcerror.h
@@ -11,7 +11,9 @@
 #ifndef API_RTCERROR_H_
 #define API_RTCERROR_H_
 
+#ifdef UNIT_TEST
 #include <ostream>
+#endif  // UNIT_TEST
 #include <string>
 #include <utility>  // For std::move.
 
@@ -143,10 +145,16 @@
 // error type.
 //
 // Only intended to be used for logging/disagnostics.
-std::ostream& operator<<(std::ostream& stream, RTCErrorType error);
-
 std::string ToString(RTCErrorType error);
 
+#ifdef UNIT_TEST
+inline std::ostream& operator<<(  // no-presubmit-check TODO(webrtc:8982)
+    std::ostream& stream,         // no-presubmit-check TODO(webrtc:8982)
+    RTCErrorType error) {
+  return stream << ToString(error);
+}
+#endif  // UNIT_TEST
+
 // Helper macro that can be used by implementations to create an error with a
 // message and log it. |message| should be a string literal or movable
 // std::string.