Add NeedMBoxProtect [inset]layout option

Add NeedMBoxProtect [inset]layout option

This accesses the inulemcmd output param which protects specific commands
(\cite, \ref) in an \mbox.

This is needed in ulem and soul commands, since their complex
detokenization makes such commands (who produce multiple words via local
assignment) fail.

So now it is possible to properly support ulem and soul via
[inset]layout

Fixes a case reported in #9404