Add support for setting a custom NetEqFactory in PeerConnection level tests.

This allows running Peerconnection level tests with a custom NetEqFactory.

Bug: webrtc:11005
Change-Id: If3063cf61a6274a137e4ab74f9ec2665425f21ae
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/161307
Reviewed-by: Artem Titov <titovartem@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Ivo Creusen <ivoc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30028}

api/test/peerconnection_quality_test_fixture.h

@@ -299,6 +299,9 @@ class PeerConnectionE2EQualityTestFixture {
     // Set the audio stream for the call from this peer. If this method won't
     // be invoked, this peer will send no audio.
     virtual PeerConfigurer* SetAudioConfig(AudioConfig config) = 0;
+    // Set a custom NetEqFactory to be used in the call.
+    virtual PeerConfigurer* SetNetEqFactory(
+        std::unique_ptr<NetEqFactory> neteq_factory) = 0;
     // If is set, an RTCEventLog will be saved in that location and it will be
     // available for further analysis.
     virtual PeerConfigurer* SetRtcEventLogPath(std::string path) = 0;