Add the LCE system API

Add the link capacity estimate system API.
Remove the system API of getCarrierBandwidth() and CarrierBandwidth as
they are replaced by the new LCE system API in PhoneStateListener.

Bug: 180434672
Bug: 176814680
Test: manual test of the new LCE system API in LinkBandwidthEstimator
Test: atest -c PhoneStateListenerTest

Merged-In: I5899acf02006a164e31f9b82aeaa7974dd6d2869
Change-Id: I5899acf02006a164e31f9b82aeaa7974dd6d2869