hgweb: perform all parameter lookup via qsparams
I think I managed to update all call sites using wsgirequest.form
to use parsedrequest.qsparams.
Since behavior of qsparams is to retrieve last value, behavior will
change if a parameter was specified multiple times. But I think this
is acceptable.
I'm not a fan of the `req.req.qsparams` pattern. And some of the
modified code could be written better. But I was aiming for a
straight port with this change. Cleanup can come later.
Differential Revision: https://phab.mercurial-scm.org/D2781
#require docutils gettext
$ $TESTDIR/check-gendoc fr
checking for parse errors