Currently, PermissionMonitor listen to user add/remove and
package add/remove intent respectively, and so does VPN.
Thus, races might occurr between them.
This commit refactor VPN part by using ConnectivityService to
listen to intents and dispatch events to VPN.
Bug: 118811303
Test: 1. atest FrameworksNetTests
2. manually add/remove package
3. cts-tradefed run cts -m CtsHostsideNetworkTests
Change-Id: Id76fd77c5fcfb2b0e21f211f63f007b1ea1aa53f
47311631d8