media download controls i18n

fixes #4015
// FREEBIE

res/values/strings.xml

@@ -872,6 +872,11 @@
     <string name="preferences__enable_if_your_device_supports_sms_mms_delivery_over_wifi">Enable if your device uses SMS/MMS delivery over WiFi (only enable when \'WiFi Calling\' is enabled on your device)</string>
     <string name="preferences_app_protection__blocked_contacts">Blocked contacts</string>
     <string name="preferences_notifications__display_in_notifications">Display in notifications</string>
+    <string name="preferences_chats__when_using_mobile_data">When using mobile data</string>
+    <string name="preferences_chats__when_using_wifi">When using Wi-Fi</string>
+    <string name="preferences_chats__when_roaming">When roaming</string>
+    <string name="preferences_chats__media_auto_download">Media auto-download</string>
+    <string name="preferences_chats__message_trimming">Message trimming</string>
 
     <!-- **************************************** -->
     <!-- menus -->

res/xml/preferences_chats.xml

@@ -1,9 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
 
 <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
-    <PreferenceCategory android:key="media_download" android:title="Media auto-download">
+    <PreferenceCategory android:key="media_download" android:title="@string/preferences_chats__media_auto_download">
         <com.h6ah4i.android.compat.preference.MultiSelectListPreferenceCompat
-                android:title="When using mobile data"
+                android:title="@string/preferences_chats__when_using_mobile_data"
                 android:key="pref_media_download_mobile"
                 android:defaultValue="@array/pref_media_download_mobile_data_default"
                 android:persistent="true"
@@ -11,7 +11,7 @@
                 android:entryValues="@array/pref_media_download_entries" />
 
         <com.h6ah4i.android.compat.preference.MultiSelectListPreferenceCompat
-                android:title="When using Wi-Fi"
+                android:title="@string/preferences_chats__when_using_wifi"
                 android:key="pref_media_download_wifi"
                 android:defaultValue="@array/pref_media_download_wifi_default"
                 android:persistent="true"
@@ -19,7 +19,7 @@
                 android:entryValues="@array/pref_media_download_entries" />
 
         <com.h6ah4i.android.compat.preference.MultiSelectListPreferenceCompat
-                android:title="When roaming"
+                android:title="@string/preferences_chats__when_roaming"
                 android:key="pref_media_download_roaming"
                 android:defaultValue="@array/pref_media_download_roaming_default"
                 android:persistent="true"
@@ -27,7 +27,7 @@
                 android:entryValues="@array/pref_media_download_entries" />
     </PreferenceCategory>
 
-    <PreferenceCategory android:key="message_trimming" android:title="Message trimming">
+    <PreferenceCategory android:key="message_trimming" android:title="@string/preferences_chats__message_trimming">
         <org.thoughtcrime.securesms.components.SwitchPreferenceCompat
             android:defaultValue="false"
             android:key="pref_trim_threads"