Add Signal Strength to TelephonyMetrics when Data Stall

Bug: 144804770
Test: 1. Build pass.
      2. We can see the SignalStrength when calling doRecovery().
      3. atest DcTrackerTest

      Test Log:
      12-18 16:00:23.398  3661  3661 D DCT-C   : trigger data stall recovery
      12-18 16:00:23.477  3661  3661 D DCT-C   : doRecovery() signalStrength:4
      12-18 16:00:23.478  3661  3661 D DCT-C   : doRecovery() get data call list
      12-18 16:00:33.737  3661  3661 D DCT-C   : trigger data stall recovery
      12-18 16:00:33.748  3661  3661 D DCT-C   : doRecovery() signalStrength:4
      12-18 16:00:33.749  3661  3661 D DCT-C   : doRecovery() get data call list

Change-Id: I5b13d62aa8e9375e1db6aff8f639d0827aca8b9a