Add language and remove scope in radio alert

Add language field for radio alert to indicate the language
of alert message. Remove scope since its value is always
public in radio alert standard.

Bug: 361348719
Flag: android.hardware.radio.hd_radio_emergency_alert_system
Test: atest android.hardware.radio.RadioManagerTest
Change-Id: I6a3e59249126767f344bb59e58d6d69a219e15cc