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
Change-Id: Id613dc152e524045a89295e5dd03171b22377e16