Re-internalize MobileState and State from SettingsLib

ConnectivityState (nee State) lived in SettingsLib because of the fact
that MobileMappings needed the MobileIconGroup class, which lived inside
of SignalIcon.java. The whole thing is a bit messy, but this CL moves
the state objects back into the connectivity package where they belong.

Also move MobileState and WifiState into their own kotlin classes.

Bug: 197851948
Test: atest SystemUITests
Change-Id: I2997c66dbffb5e44b8f53b9020cdeb8b614cea3b