new public API and AIDL to get and listen for signal strength changes.

Below public APIs are added
  requestNtnSignalStrength()
  registerForNtnSignalStrengthChanged()
  unregisterForNtnSignalStrengthChanged()

Bug: 301511156
Test: SatelliteManagerTest, SatelliteControllerTest,
SatelliteManagerTestOnMockService

Change-Id: I08490bb8b7bc5bcd27eacc153750b957741670ac