Improve lifecycle of ZenModeFragment & friends

* Don't keep Settings observers longer than start-stop.
* Only call updateState() once on controllers during create->start->resume.
* Remove some duplicate controller update methods from ZenModesFragmentBase (we can directly call DashboardFragment's).
* Don't update controllers if unrelated modes were changed.
* Extract ZenSettingsObserver for use in the link tile later.
* Add tests.

Fixes: 353946788
Test: atest com.android.settings.notification.modes
Flag: android.app.modes_ui
Change-Id: I64b51714d699b5c3a592a76fcb615d2999998829

src/com/android/settings/notification/modes/ManualDurationPreferenceController.java

@@ -18,6 +18,7 @@ package com.android.settings.notification.modes;
 
 import android.content.Context;
 
+import androidx.annotation.NonNull;
 import androidx.fragment.app.Fragment;
 import androidx.preference.Preference;
 import androidx.preference.PreferenceScreen;
@@ -49,12 +50,12 @@ public class ManualDurationPreferenceController extends AbstractZenModePreferenc
         return zenMode.isManualDnd();
     }
 
-    // Called by parent fragment onAttach().
+    // Called by parent fragment onStart().
     void registerSettingsObserver() {
         mSettingsObserver.register();
     }
 
-    // Called by parent fragment onDetach().
+    // Called by parent fragment onStop().
     void unregisterSettingsObserver() {
         mSettingsObserver.unregister();
     }
@@ -69,7 +70,7 @@ public class ManualDurationPreferenceController extends AbstractZenModePreferenc
     }
 
     @Override
-    public void updateState(Preference preference, ZenMode unusedZenMode) {
+    public void updateState(Preference preference, @NonNull ZenMode unusedZenMode) {
         // This controller is a link between a Settings value (ZEN_DURATION) and the manual DND
         // mode. The status of the zen mode object itself doesn't affect the preference
         // value, as that comes from settings; that value from settings will determine the