accessibilify quiz unlocking
accessibilify quiz unlocking

closes CNVS-19328
refs CNVS-15543

This applies a screenreader-only label to the datetime picker
used in the Quiz Unlocking UI, and some KB-only user tooltips
(though they are visible for all users).  The goal is to make
it clear what format to input dates and times in to users
for whom the rich selector isn't so great.

TEST PLAN:
- go to /courses/x/quizzes/y
- lock the quiz now
- unlock the quiz now (dialog should come up)
- Using a screenreader with your eyes closed, ensure you can figure out
  what date format to use for the unlock target
- tab through to the same field and prove that you see
  a little tooltip telling you what format to enter the date and time
in.

Change-Id: If6b4cfdd56b49c7e6b5824744833ed4eb5196776
Reviewed-on: https://gerrit.instructure.com/56643
Tested-by: Jenkins
Reviewed-by: Jason Madsen <bcb5fff571a20f07c35d17ba9c364855c776dce7@instructure.com>
QA-Review: Jeremy Putnam <b030d6d6f199f844ec424882be473c2ab9adc93b@instructure.com>
Product-Review: Ethan Vizitei <73eeb0b2f65d05a906adf3b21ee1f9f5a2aa3c1c@instructure.com>

utkarshx/canvas-lms,ShreniiNepal/shrenii_lmp,ShreniiNepal/shrenii_lmp,wrdsb/canvas-lms,whalejasmine/canvas-lms,instructure/canvas-lms,grahamb/canvas-lms,Rvor/canvas-lms,tgroshon/canvas-lms,leftplusrightllc/canvas-lms,dgynn/canvas-lms,venturehive/canvas-lms,SwinburneOnline/canvas-lms,narigone/canvas,sfu/canvas-lms,fronteerio/canvas-lms,dgynn/canvas-lms,antoniuslin/canvas-lms,sfu/canvas-lms,Rvor/canvas-lms,eCNAP/CANVAS,HotChalk/canvas-lms,roxolan/canvas-lms,instructure/canvas-lms,HotChalk/canvas-lms,AndranikMarkosyan/lms,HotChalk/canvas-lms,dgynn/canvas-lms,narigone/canvas,AndranikMarkosyan/lms,fronteerio/canvas-lms,tgroshon/canvas-lms,AndranikMarkosyan/lms,ShreniiNepal/shrenii_lmp,sfu/canvas-lms,juoni/canvas-lms,venturehive/canvas-lms,utkarshx/canvas-lms,shidao-fm/canvas-lms,eCNAP/CANVAS,wrdsb/canvas-lms,antoniuslin/canvas-lms,kyroskoh/canvas-lms,SwinburneOnline/canvas-lms,wrdsb/canvas-lms,jay3126/canvas-lms,redconfetti/canvas-lms,instructure/canvas-lms,snehakachroo1/LSI_replica,fronteerio/canvas-lms,redconfetti/canvas-lms,sdeleon28/canvas-lms,grahamb/canvas-lms,efrj/canvas-lms,efrj/canvas-lms,matematikk-mooc/canvas-lms,shidao-fm/canvas-lms,grahamb/canvas-lms,leftplusrightllc/canvas-lms,dgynn/canvas-lms,instructure/canvas-lms,juoni/canvas-lms,greyhwndz/canvas-lms,juoni/canvas-lms,djbender/canvas-lms,matematikk-mooc/canvas-lms,narigone/canvas,tgroshon/canvas-lms,efrj/canvas-lms,tgroshon/canvas-lms,kyroskoh/canvas-lms,djbender/canvas-lms,whalejasmine/canvas-lms,redconfetti/canvas-lms,matematikk-mooc/canvas-lms,antoniuslin/canvas-lms,Jyaasa/canvas-lms,leftplusrightllc/canvas-lms,djbender/canvas-lms,SwinburneOnline/canvas-lms,snehakachroo1/LSI_replica,SwinburneOnline/canvas-lms,skmezanul/canvas-lms,kyroskoh/canvas-lms,sdeleon28/canvas-lms,leftplusrightllc/canvas-lms,efrj/canvas-lms,utkarshx/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,AndranikMarkosyan/lms,antoniuslin/canvas-lms,sfu/canvas-lms,roxolan/canvas-lms,skmezanul/canvas-lms,eCNAP/CANVAS,Jyaasa/canvas-lms,sfu/canvas-lms,jay3126/canvas-lms,wrdsb/canvas-lms,grahamb/canvas-lms,jay3126/canvas-lms,whalejasmine/canvas-lms,kyroskoh/canvas-lms,roxolan/canvas-lms,fronteerio/canvas-lms,Jyaasa/canvas-lms,jay3126/canvas-lms,narigone/canvas,sdeleon28/canvas-lms,sdeleon28/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,Rvor/canvas-lms,greyhwndz/canvas-lms,djbender/canvas-lms,snehakachroo1/LSI_replica,shidao-fm/canvas-lms,eCNAP/CANVAS,whalejasmine/canvas-lms,roxolan/canvas-lms,juoni/canvas-lms,ShreniiNepal/shrenii_lmp,skmezanul/canvas-lms,Jyaasa/canvas-lms,Rvor/canvas-lms,HotChalk/canvas-lms,venturehive/canvas-lms,shidao-fm/canvas-lms,redconfetti/canvas-lms,matematikk-mooc/canvas-lms,greyhwndz/canvas-lms,utkarshx/canvas-lms,skmezanul/canvas-lms,greyhwndz/canvas-lms,instructure/canvas-lms,snehakachroo1/LSI_replica,instructure/canvas-lms