Deprecate PeerConnectionFactory::CreatePeerConnection

Applications should use CreatePeerConnectionOrError instead.

Moved fallback implementations of CreatePeerConnection into the
api/peer_connection_interface.h file, so that we do not have to
declare these methods in the proxy.

Bug: webrtc:12238
Change-Id: I70c56336641c2a108b68446ae41f43409277a584
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/217762
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33964}
diff --git a/test/network/network_emulation_pc_unittest.cc b/test/network/network_emulation_pc_unittest.cc
index 6420e36..bd15b5a 100644
--- a/test/network/network_emulation_pc_unittest.cc
+++ b/test/network/network_emulation_pc_unittest.cc
@@ -99,7 +99,12 @@
     rtc_configuration.servers.push_back(server);
   }
 
-  return pcf->CreatePeerConnection(rtc_configuration, std::move(pc_deps));
+  auto result =
+      pcf->CreatePeerConnectionOrError(rtc_configuration, std::move(pc_deps));
+  if (!result.ok()) {
+    return nullptr;
+  }
+  return result.MoveValue();
 }
 
 }  // namespace