Implement (mostly) standards-compliant RTCIceTransportState.

In order to correctly implement RTCPeerConnectionState and RTCIceConnectionState the ice transports need to support RTCIceTransportState.
This CL adds an implementation parallel to the current non-standard IceTransportState. It's not currently used anywhere. The old implementation will remain in place until we're ready to switch RTCIceConnectionState over.

Bug: webrtc:9308
Change-Id: I30e2bbb5b4fafa410261bcd9d5e3b76c03435feb
Reviewed-on: https://webrtc-review.googlesource.com/c/103220
Reviewed-by: Qingsi Wang <qingsi@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Jonas Olsson <jonasolsson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25078}
diff --git a/p2p/BUILD.gn b/p2p/BUILD.gn
index 2d351bb..5d4e706 100644
--- a/p2p/BUILD.gn
+++ b/p2p/BUILD.gn
@@ -86,6 +86,7 @@
   deps = [
     "../api:libjingle_peerconnection_api",
     "../api:ortc_api",
+    "../api/transport:enums",
     "../logging:ice_log",
     "../rtc_base:checks",
     "../rtc_base:rtc_base",