Add 'Recent Conversations' to the conversation page

Test: atest
Bug: 171191376
Change-Id: Id7208312dff0cc022c2f16b3872fae1a9dc09ed7

res/layout/conversations_clear_recents.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright (C) 2020 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.
+  -->
+
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="vertical">
+    <Button
+        android:id="@+id/conversation_settings_clear_recents"
+        style="@style/ActionPrimaryButton"
+        android:layout_marginStart="@dimen/screen_margin_sides"
+        android:layout_marginEnd="@dimen/description_margin_sides"
+        android:layout_marginTop="@dimen/zen_mode_settings_button_margin_vertical"
+        android:layout_marginBottom="@dimen/zen_mode_settings_button_margin_vertical"
+        android:text="@string/conversation_settings_clear_recents"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"/>
+
+</LinearLayout>

res/layout/preference_widget_clear.xml

@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright (C) 2020 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.
+  -->
+
+<!-- Settings button -->
+<ImageView
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/clear_button"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:layout_gravity="center"
+    android:paddingStart="?android:attr/listPreferredItemPaddingEnd"
+    android:paddingEnd="?android:attr/listPreferredItemPaddingEnd"
+    android:background="?android:attr/selectableItemBackground"
+    android:scaleType="center"
+    android:src="@drawable/ic_clear"
+    android:contentDescription="@string/clear" />