Extend NetworkRoute with more info about local/remote endpoints

This patch extends the NetworkRoute struct with more information
about local/remote endpoints. It adds
- adapter type
- adapter id
- relay

(previously it was "only" network_id)

The patch leaves the {local/remote}_network_id fields
around and populated since downstream projects depend
on them. They will be removed once they have migrated.

OWNER: srte@ call/ test/
OWNER: asapersson@ video/
OWNER: hta@ p2p/ pc/ rtc_base/

BUG: webrtc:11434
Change-Id: I9bcec385b40d707db385fef40b2c7a315dd35dd0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/170628
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Commit-Queue: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30848}

rtc_base/network_constants.h

@@ -13,6 +13,8 @@
 
 #include <stdint.h>
 
+#include <string>
+
 namespace rtc {
 
 static const uint16_t kNetworkCostMax = 999;
@@ -37,6 +39,8 @@ enum AdapterType {
   ADAPTER_TYPE_ANY = 1 << 5,
 };
 
+std::string AdapterTypeToString(AdapterType type);
+
 }  // namespace rtc
 
 #endif  // RTC_BASE_NETWORK_CONSTANTS_H_