Messaging: Remove setHost() logic

* This relies too much on call order and other things to go right
* We can use the activity just fine for it

Fixes: https://gitlab.com/LineageOS/issues/android/-/issues/8623
Change-Id: I048910258cedaa21e26fb88a57e5028ae1df9f83

res/layout/conversation_list_activity.xml

@@ -1,24 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!--
-    Copyright (C) 2015 The Android Open Source Project
-    Copyright (C) 2025 The LineageOS 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.
--->
-<androidx.fragment.app.FragmentContainerView
-    xmlns:android="http://schemas.android.com/apk/res/android"
-    android:name="com.android.messaging.ui.conversationlist.ConversationListFragment"
-    android:id="@+id/conversation_list_fragment"
-    android:theme="@style/Theme.MaterialComponents.Light.DarkActionBar"
-    android:layout_width="match_parent"
-    android:layout_height="match_parent" />