[Settings] Use background thread to get VoNr state.

 - TelephonyManager#isVoNrEnabled may not send back the result in time,
   so use different thread and timer to prevent ANR.

Bug: 282876876
Test: atest passed
Change-Id: Ie6cc0f8a459f5ebed930e457dacb9b742df70fad
2 files changed