UserDetailsSettings uses Guest string, not Guest name

The UserDetailsSettings panel, and its title, show the user's UserInfo.name.
This is correct for a regular user (and for the Owner). But for a Guest user,
this is incorrect, and the user_guest string should be used instead.

The difference occurs if the system language is changed after the guest is created;
the word 'guest' should update to the current language, not be frozen to the
language at the time of the guest's creation.

Bug: 185309160
Test: atest UserDetailsSettingsTest
Change-Id: I545aa3e6cc5d00c0bcc49960f37dddd9334b153b

src/com/android/settings/users/UserDetailsSettings.java

@@ -206,7 +206,7 @@ public class UserDetailsSettings extends SettingsPreferenceFragment
 
         mSwitchUserPref.setTitle(
                 context.getString(com.android.settingslib.R.string.user_switch_to_user,
-                        mUserInfo.name));
+                        UserSettings.getUserName(context, mUserInfo)));
 
         if (mUserCaps.mDisallowSwitchUser) {
             mSwitchUserPref.setDisabledByAdmin(RestrictedLockUtilsInternal.getDeviceOwner(context));