Fix accessibility issues with gradebook CSV import
Fix accessibility issues with gradebook CSV import

Fixes CNVS-29914

This adds some context to select menu options so screenreader users
know what they are selecting and ties a label to its input field.

Test plan:
* Enable VoiceOver or another screenreader
* Import a CSV with an unknown student name and unknown assignment
* On the clarification page, navigate the form elements via VO

You should hear Choose student or assignment rather than just "Choose"
on the menu options and when navigating to the points possible input,
you should hear "points possible."

Change-Id: Ibd3575514a778657078a35cb4bb6e1291378af28
Reviewed-on: https://gerrit.instructure.com/82877
Tested-by: Jenkins
Reviewed-by: Cameron Matheson <1d572acbfa68c7c6e541c7b840d6b622e5c0dc91@instructure.com>
QA-Review: Amber Taniuchi <ef4bfd1e6d278f6bc7d4a478f02be2cb9581a0a5@instructure.com>
Product-Review: Nathan Rogowski <2e8aa918660411855c6d44d5bb2da677aa033255@instructure.com>

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