Reland "Adds PeerConnection scenario test framework."

This is a reland of ad5c4accad00e04de08e2b62d366cc1f8e0320a5

It was flaky due to starting ICE signaling before SDP negotiation
finished. This was solved by adding an helper for adding ice candidates
which will wait until the peer connection is ready if needed.

Original change's description:
> Adds PeerConnection scenario test framework.
>
> Bug: webrtc:10839
> Change-Id: If67eeb680d016d66c69d8e761a88c240e4931a5d
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/147276
> Commit-Queue: Sebastian Jansson <srte@webrtc.org>
> Reviewed-by: Steve Anton <steveanton@webrtc.org>
> Reviewed-by: Erik Språng <sprang@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#28754}

Bug: webrtc:10839
Change-Id: I6eb8f482561c87e7b0f20d2431d21a41b26c91d5
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/147877
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28777}
diff --git a/test/BUILD.gn b/test/BUILD.gn
index 5af4766..a16c465 100644
--- a/test/BUILD.gn
+++ b/test/BUILD.gn
@@ -390,6 +390,7 @@
       "../rtc_base/system:file_wrapper",
       "../test:single_threaded_task_queue",
       "pc/e2e:e2e_unittests",
+      "peer_scenario/tests",
       "scenario:scenario_unittests",
       "time_controller",
       "time_controller:time_controller_unittests",