Added device state monitor

Added DeviceStateMonitor to replace the legacy screen state RIL
API. Instead of sending the screen state to the modem, the new
device state monitor can explicitly turn on/off the unsolicited
response from the modem based on difference scenarios (e.g.
tethering, charging, screen state). It also sends more device
state to the modem including charging state, power saving state,
and low data expected state.

Note that in order to support the old vendor RIL, framework will
still invoke the legacy screen state API to ensure the best
user experience on those devices.

Test: Manual. Unit tests.
bug: 32223897, 20125037, 28294587

Merged-In: I76ce307bde1d3160af2ac44a57f101e4cafc7ae4
Change-Id: I76ce307bde1d3160af2ac44a57f101e4cafc7ae4