Pass MediaTransportFactory to PeerConnectionFactory.

And use RTCConfiguration to enable/disable it on a per connection basis.

With the advent of MediaTransportInterface, we need to be able to enable
it on the per PeerConnection basis.

At this point PeerConnection will not take any action when the
MediaTransportInterface is set; this code will land a bit later, and
will be accompanied by the tests that verify correct setup (hence no tests right now).

At this point this is just a method stub to enable further development.

Bug: webrtc:9719
Change-Id: I1f77d650cb03bf1191aa0b35669cd32f1b68446f
Reviewed-on: https://webrtc-review.googlesource.com/c/103860
Reviewed-by: Bjorn Mellem <mellem@webrtc.org>
Reviewed-by: Anton Sukhanov <sukhanov@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25053}
diff --git a/sdk/BUILD.gn b/sdk/BUILD.gn
index c4bee38..b259f51 100644
--- a/sdk/BUILD.gn
+++ b/sdk/BUILD.gn
@@ -1170,6 +1170,7 @@
           ":videoframebuffer_objc",
           ":videosource_objc",
           ":videotoolbox_objc",
+          "../api:libjingle_peerconnection_api",
           "../api/audio_codecs:audio_codecs_api",
           "../api/audio_codecs:builtin_audio_decoder_factory",
           "../api/audio_codecs:builtin_audio_encoder_factory",