Update ltx to v3.0.0 - Githubissues

Removes @xmpp/xml/lib/serialize use ltx.stringify
Removes @xmpp/xml/lib/clone use ltx.clone
See ltx 3 relesae notes https://github.com/xmppjs/ltx/releases/tag/v3.0.0
Reduces browser bundle
Fix @xmpp/debug adding parent xmlns to children see https://github.com/xmppjs/xmpp.js/issues/890#issuecomment-902853512

xmppjs / xmpp.js