Adds WebRtcKeyValueConfig interface

The WebRtcKeyValueConfig interface allows providing custom key value
configurations that changes per instance of GoogCcNetworkController.

Bug: webrtc:10009
Change-Id: I520fff030d1c3c755455ec8f67896fe8a6b4d970
Reviewed-on: https://webrtc-review.googlesource.com/c/116989
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26312}
diff --git a/rtc_tools/BUILD.gn b/rtc_tools/BUILD.gn
index b77d671..4e9e3cf 100644
--- a/rtc_tools/BUILD.gn
+++ b/rtc_tools/BUILD.gn
@@ -260,6 +260,7 @@
 
         # TODO(kwiberg): Remove this dependency.
         "../api/audio_codecs:audio_codecs_api",
+        "../api/transport:field_trial_based_config",
         "../api/transport:goog_cc",
         "../call:call_interfaces",
         "../call:video_stream_api",