DA - split large hashes

fixes CNVS-16452

test plan:
  - regression test of the following
    - GB csv download/upload
    - assignments index
    - assignments api index
    - submissions api call to for_students
      - as teacher/observer/student
    - score calculation in GB
    - score calculation on individual grades page

Change-Id: Ifaa0c7580535c2c5d4e218508ef00c1b6007770b
Reviewed-on: https://gerrit.instructure.com/43361
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cameron Sutter <csutter@instructure.com>
QA-Review: Sean Lewis <slewis@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>