[Catalyst] Update PreferenceLifecycleContext.notifyPreferenceChange

Change the signature from metadata to preference key, so that the API
could be used to notify other preferences on the same screen.

NO_IFTTT=Catalyst only

Bug: 332201912
Flag: com.android.settings.flags.catalyst
Test: atest
Change-Id: Ibdf5f9004471d5491a0be1e84365cbe9f136c373

src/com/android/settings/datausage/DataSaverMainSwitchPreference.kt

@@ -32,7 +32,7 @@ class DataSaverMainSwitchPreference(context: Context) :
     private var dataSaverBackendListener: DataSaverBackend.Listener? = null
 
     override val key
-        get() = "use_data_saver"
+        get() = KEY
 
     override val title
         get() = R.string.data_saver_switch_title
@@ -46,7 +46,7 @@ class DataSaverMainSwitchPreference(context: Context) :
         ReadWritePermit.ALLOW
 
     override fun onStart(context: PreferenceLifecycleContext) {
-        val listener = DataSaverBackend.Listener { context.notifyPreferenceChange(this) }
+        val listener = DataSaverBackend.Listener { context.notifyPreferenceChange(KEY) }
         dataSaverBackendListener = listener
         dataSaverBackend.addListener(listener)
     }
@@ -71,4 +71,8 @@ class DataSaverMainSwitchPreference(context: Context) :
             dataSaverBackend.isDataSaverEnabled = value as Boolean
         }
     }
+
+    companion object {
+        const val KEY = "use_data_saver"
+    }
 }