voicemail notification settings cleanup

- remove UI preference for voicemail notification ringtone & vibration
settings as they are not functioning with notification channel
introduced
- have a new Notification Preference under voicemailSettings which will
navigate to the system settings screen for that channel.
- modify telephonymanager API getVoiceMailRingToneUri and
isVoiceMailVibrationEnabled from sharedPreference to NotificationChannel
data.
- more cleanup work needed till next API bump for telephonyManager APIs
setVoicemailVibrationEnabled and setVoicemailRingToneUri

Bug: 37912316
Test: Manaul test
Change-Id: I869362d7d4ccf563e92d358117948aea028bdd37
diff --git a/res/xml/voicemail_settings.xml b/res/xml/voicemail_settings.xml
index 1fc1fe1..021a764 100644
--- a/res/xml/voicemail_settings.xml
+++ b/res/xml/voicemail_settings.xml
@@ -50,14 +50,7 @@
 
     </PreferenceScreen>
 
-    <com.android.phone.settings.VoicemailRingtonePreference
-        android:key="@string/voicemail_notification_ringtone_key"
-        android:title="@string/voicemail_notification_ringtone_title"
-        android:persistent="false"
-        android:ringtoneType="notification" />
-
-    <SwitchPreference
-        android:key="@string/voicemail_notification_vibrate_key"
-        android:title="@string/voicemail_notification_vibrate_when_title"
-        android:persistent="true" />
+    <Preference
+        android:key="@string/voicemail_notifications_key"
+        android:title="@string/voicemail_notifications_preference_title"/>
 </PreferenceScreen>