Make getOperatorAlphaLongRaw/getOperatorAlphaShortRaw as public APIs

This is as per API council feedback

Bug: 147676513
Test: Verified system UI with AT&T SIM
      atest SystemUITests
      atest frameworks/opt/telephony/tests/telephonytests/

Change-Id: Ie000a736831c8cd806a7e53d9fd56e3e3b707a88