break up long quizzes selenium specs into many files

fixes CNVS-15691

files won't be parallelized
by testbot, so when they get really big
they prevent us from taking full advantage of
the performance available.  this helps our ability
to speed up builds by splitting up the longest
running quizzes selenium specs into smaller files
that can be parallelized.

TEST PLAN: only changes specs; if specs
are passing, we're good

Change-Id: I3724658b32b1f58126a0827eedca68e6f72cd94a
Reviewed-on: https://gerrit.instructure.com/41754
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
QA-Review: Ethan Vizitei <evizitei@instructure.com>
Product-Review: Ethan Vizitei <evizitei@instructure.com>