Create a new region picker page

1. The region which is selected in region picker will also apply to the first locale.
2. When a user change the first locale, the region of the first locale will be updated to the region picker.

Bug: 385047778
Flag: com.android.settings.flags.regional_preferences_api_enabled
Test: check hsv
Change-Id: I001e0910ce9d1601513ed2f52e6ee30d3551859f

src/com/android/settings/regionalpreferences/RegionPreferenceController.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.regionalpreferences;
+
+import android.content.Context;
+
+import androidx.annotation.NonNull;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceScreen;
+
+import com.android.internal.app.LocaleStore;
+import com.android.settings.core.BasePreferenceController;
+import com.android.settings.flags.Flags;
+
+import java.util.Locale;
+
+/** A controller for the entry of region picker page */
+public class RegionPreferenceController extends BasePreferenceController {
+
+    public RegionPreferenceController(@NonNull Context context, @NonNull String key) {
+        super(context, key);
+    }
+
+    @Override
+    public void displayPreference(@NonNull PreferenceScreen screen) {
+        super.displayPreference(screen);
+        Preference preference = screen.findPreference(getPreferenceKey());
+        LocaleStore.LocaleInfo localeInfo = LocaleStore.getLocaleInfo(Locale.getDefault());
+        preference.setSummary(localeInfo.getFullCountryNameNative());
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        if (!Flags.regionalPreferencesApiEnabled()) {
+            return CONDITIONALLY_UNAVAILABLE;
+        }
+        return AVAILABLE;
+    }
+}