Add Message::listParam()
This allows for passing a list of values that will be turned into a list
in the context of the language for which the Message is being processed.
For example, currently you'd have to do
$msg = new Message( 'something', [ $language->commaList( $list ) ] );
which isn't going to give correct results if the message is later
changed to a different language with a different value for
'comma-separator'.
Now, you can do this instead
$msg = new Message( 'something', [ Message::listParam( $list, 'comma' ) ] );
and it will be listified properly no matter what language is later used to
parse $msg.
Change-Id: I66868c61832260870449998fef14c842f17753ee