Add a turn port prune policy to keep the first ready turn port.

Bug: webrtc:11026
Change-Id: I6222e9613ee4ce2dcfbb717e2430ea833c0dc373
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/155542
Commit-Queue: Honghai Zhang <honghaiz@webrtc.org>
Reviewed-by: Qingsi Wang <qingsi@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Reviewed-by: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29470}
diff --git a/api/BUILD.gn b/api/BUILD.gn
index 58fd04e..4eed48c 100644
--- a/api/BUILD.gn
+++ b/api/BUILD.gn
@@ -181,6 +181,7 @@
     "task_queue",
     "transport:bitrate_settings",
     "transport:datagram_transport_interface",
+    "transport:enums",
     "transport:network_control",
     "transport/media:audio_interfaces",
     "transport/media:media_transport_interface",