Preview quiz: show the correct points possible

Closes CNVS-3856

TEST PLAN
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  - create a quiz with 3 questions with points possible: 0.42, 0.23, 1
  - preview the quiz and get all the questions correctly
    - verify you see "1.65 out of 1.65"
  - retry with failing some questions
    - verify you get the correct score shown

Change-Id: Ib7e830adce26b2c2346eb3a4149e4bc0406a9d35
Reviewed-on: https://gerrit.instructure.com/39295
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Reviewed-by: Ryan Taylor <rtaylor@instructure.com>
Reviewed-by: Josh Simpson <jsimpson@instructure.com>
Product-Review: Ahmad Amireh <ahmad@instructure.com>