Update CarrierSignalAgent with new CarrierConfigManager APIs

Improve the performance of CarrierSignalAgent by:
- Replacing carrier config change broadcast receiver with listener
  which has much lower lagency.
- Retrieving subset carrier configs as needed to save memory

Bug: 244087782
Test: atest CarrierSignalAgentTest
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:16e659fdd442fca1dc76c172eeb740153655ec9a)
Merged-In: I7df0840f9645a2d0462ab13d6bb083dbbcfac3a8

Change-Id: Ic05a9e1d7df5f964b396f57eaa77bc43515d816e