Add areLongLivedTcpConnectionsExpensive in VpnTransportInfo

Add VpnTransportInfo.areLongLivedTcpConnectionsExpensive() in API
surface to allow privileged apps to know whether the long-lived
TCP connections should be expensive in the VPN network.

This is expected to be used combined with getBypassable()
because connections should always go through a VPN that is not
bypassable.

Bug: 259000745
Test: atest FrameworksNetTests
Change-Id: Ic9bcdf43f252f22d12a1136902cc8bbf9cc731f5
diff --git a/framework/api/system-current.txt b/framework/api/system-current.txt
index c7872a0..0b0f2bb 100644
--- a/framework/api/system-current.txt
+++ b/framework/api/system-current.txt
@@ -512,7 +512,8 @@
   }
 
   public final class VpnTransportInfo implements android.os.Parcelable android.net.TransportInfo {
-    ctor public VpnTransportInfo(int, @Nullable String, boolean);
+    ctor public VpnTransportInfo(int, @Nullable String, boolean, boolean);
+    method public boolean areLongLivedTcpConnectionsExpensive();
     method public int describeContents();
     method public boolean getBypassable();
     method public int getType();