Add a Carrier-config specific ratcheter of RATs.

Only reports transitions to higher RATs within a given family.
Reset when we move to a new cell.
Avoids costly propogation of RAT flapping within the family,
for example every outgoing data pops us into a higher RAT and
idle time pops us back down.

bug:27360321
Change-Id: Ifd219eda701eb2c87a8b6798d919f71fab804f5d