Handle when non-emergency call fails and no 2G

When a non-emergency call fails and 2G is disabled, we want to surface
to the user that 2G was previously disabled on their device and it could
be impacting their connectivity. This change updates DisconnectCauseUtil
and TelephonyConnection to facilitate this.

Test: manual & atest TelephonyConnectionServiceTest DisconnectCauseUtilTest
Bug: b/300142897
Change-Id: Iec34dd87addd9f48191aeb3e25b60d03d533c23f
4 files changed