Roll forward to cl/338725629

Signed-off-by: hai007 <hais@google.com>

cpp/core/core.h

@@ -215,6 +215,9 @@ class Core {
   void InitiateBandwidthUpgrade(absl::string_view endpoint_id,
                                 ResultCallback callback);
 
+  // Gets the local endpoint generated by Nearby Connections.
+  std::string GetLocalEndpointId() { return client_.GetLocalEndpointId(); }
+
  private:
   static constexpr absl::Duration kWaitForDisconnect = absl::Milliseconds(5000);