Add button for activating modes manually

Fixes: 308819907
Flag: android.app.modes_ui
Test: ZenModeButtonPreferenceControllerTest
Test: atest com.android.settings.notification.modes
Change-Id: Id018d360c648dd948d2f950ca67cfbea71cc5c68

res/layout/modes_activation_button.xml

@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  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.
+  -->
+
+<FrameLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content">
+
+    <Button
+        android:id="@+id/activate_mode"
+        style="@style/ActionPrimaryButton"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"/>
+
+</FrameLayout>