Adjust the NetworkRequest configuration used by SecurityController

This change restricts the NetworkRequest used by SecurityControllerImpl
to only include network types that SecurityControllerImpl is truly
concerned about, by adding the transport type TRANSPORT_VPN.

Bug: 319197157
Test: manually check the monitored networks listed in the dumpsys output.
Change-Id: I8d93ff8ca84329a4d2ce5fa9df97131ac29ca35c