[PixelSettings] Group each preference by category and add android:key

Bug: 376172757
Test: manual
Flag: EXEMPT resource only update
Change-Id: I6bfe9f48e90f5022cf474043ff57306619d95b44

res/xml/regional_preference_main_page.xml

@@ -20,9 +20,13 @@
     android:key="regional_preferences">
 
     <com.android.settingslib.widget.TopIntroPreference
+        android:key="regional_pref_intro"
         android:title="@string/regional_preferences_main_page_sub_title"
         android:persistent="false"/>
 
+    <PreferenceCategory
+        android:key="regional_preferences_category"
+        android:layout="@layout/settingslib_preference_category_no_title">
         <Preference
             android:key="key_temperature_unit"
             android:title="@string/temperature_preferences_title"
@@ -55,6 +59,7 @@
                 android:name="arg_key_regional_preference"
                 android:value="arg_value_language_select"/>
         </Preference>
+    </PreferenceCategory>
 
     <com.android.settingslib.widget.FooterPreference
         android:key="regional_pref_footer"

res/xml/regional_preferences_first_day_of_week.xml

@@ -21,6 +21,7 @@
     android:key="regional_preference_first_day_of_week">
 
     <com.android.settingslib.widget.TopIntroPreference
+        android:key="first_day_of_week_intro"
         android:title="@string/regional_preferences_option_page_sub_title"
         android:persistent="false" />
 

res/xml/regional_preferences_temperature.xml

@@ -21,6 +21,7 @@
     android:key="regional_preference_temperature">
 
     <com.android.settingslib.widget.TopIntroPreference
+        android:key="temperature_unit_intro"
         android:title="@string/regional_preferences_option_page_sub_title"
         android:persistent="false" />