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
a07cef1059