Publish rtc event log api and default factory for it in api/

Bug: webrtc:10206
Change-Id: I34194ddb6fd2b0a3d7c553fadc9ddc1ea9740da0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/137500
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28023}

logging/rtc_event_log/rtc_event_log_parser.h

@@ -39,6 +39,8 @@ RTC_POP_IGNORING_WUNDEF()
 
 namespace webrtc {
 
+enum PacketDirection { kIncomingPacket = 0, kOutgoingPacket };
+
 template <typename T>
 class PacketView;