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
Change-Id: I7df0840f9645a2d0462ab13d6bb083dbbcfac3a8
Merged-In: I7df0840f9645a2d0462ab13d6bb083dbbcfac3a8
(cherry picked from commit 16e659fd)