Notification Improvements

- add MediaStyle notifications for Background and Popup playback
- reduce excessive notification updating ( / recreating of Notification.Builder object) when playing background / popup media
- add new buffering state indicator (can be disabled)
- upscale close icon / downscale replay icon
- add notification slot settings
- move notification settings to appearance
- fix Metadata (song title, artist and album art) sometimes not being set correctly
- other misc notification fixes

Co-authored-by: wb9688 <wb9688@users.noreply.github.com>

app/src/main/java/org/schabi/newpipe/settings/AppearanceSettingsFragment.java

@@ -11,6 +11,7 @@ import androidx.annotation.Nullable;
 import androidx.preference.Preference;
 
 import org.schabi.newpipe.R;
+import org.schabi.newpipe.player.NotificationUtil;
 import org.schabi.newpipe.util.Constants;
 
 public class AppearanceSettingsFragment extends BasePreferenceFragment {
@@ -52,8 +53,22 @@ public class AppearanceSettingsFragment extends BasePreferenceFragment {
             final Preference captionSettings = findPreference(captionSettingsKey);
             getPreferenceScreen().removePreference(captionSettings);
         }
+
+        findPreference(getString(R.string.enable_old_notifications_key))
+                .setOnPreferenceChangeListener(oldNotificationsOnPreferenceChangeListener);
     }
 
+    private Preference.OnPreferenceChangeListener oldNotificationsOnPreferenceChangeListener
+            = (preference, newValue) -> {
+//        NotificationUtil.getInstance().toast(getContext(),
+//                "Killed background / popup player notification(s) !");
+        NotificationUtil.getInstance()
+                .cancelNotification(NotificationUtil.NOTIFICATION_ID_BACKGROUND);
+        NotificationUtil.getInstance().cancelNotification(NotificationUtil.NOTIFICATION_ID_POPUP);
+
+        return true;
+    };
+
     @Override
     public void onCreatePreferences(final Bundle savedInstanceState, final String rootKey) {
         addPreferencesFromResource(R.xml.appearance_settings);