doc: split option variants into separate items
e226f18934eb7291 modified the lei-q manpage so that each variant of an
option gets a dedicated =item to make L</--xyz> look nicer and to
follow the Perl core documentation. Do the same for the other
manpages.
Note that this still leaves the variants of an option grouped in one
scenario: when a list of options without descriptions is presented as
a pointer to another location. Splitting the variants in that case
would make it harder for the reader to tell what the distinct options
are.