Make sure XAR filter comes with Woodstox dependency

XAR input filter stream assume the XMLInputFactory is thread safe which is true in Woodstox implementation but not enforced by the XMLInputFactory specification.

XWiki do come with Woodstox but xwiki-platform-filter-stream-xar does not enforce it which would be safer. It also means that right now xwiki-platform-filter-stream-xar test are not executed with woodstox so they don't reflex the runtime behavior.