CTS test for VPN lockdown whitelist.

The test ensures that:

1. If VPN in lockdown mode is down (service not running),
   apps have no connectivity.
2. If the app is whitelisted, it has connectivity.
3. When the service starts, whitelisted app switches to VPN.
4. Whitelist is preserved across reboot.

Bug: 77468593
Test: atest MixedDeviceOwnerTest#testAlwaysOnVpn
atest MixedDeviceOwnerTest#testAlwaysOnVpnAcrossReboot
Change-Id: Ib5aad289fbbaad65f98c0a0edadde5eaf9f9bd9d
5 files changed