DPM API to set Wi-Fi minimum security level required

Adding API for the admin to set the mininum security level required
for a Wi-Fi network in order to be elligible for a connection.

Bug: 197558754
Test: atest com.android.server.devicepolicy.DevicePolicyManagerTest
Change-Id: I90abb4e3ce9597cb4bff57a6f9e1e8d4a097ed3e
6 files changed