Create NetworkProviderSettings for provider model

Provider model is a feature which improves networks
Settings UX.

NetworkProviderSettings is the fragment which allow
users to choose a mobile network or a Wi-Fi network
to connect.

At this change, NetworkProviderSettings is a clone
of WifiSettings, mobile networks will be integrated
at later CLs.

Bug: 167474581
Test: make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.network.NetworkProviderSettingsTest
Change-Id: I185639a8f2469e9ec76ad18b6c2bc2e8a4d079e3