Quiz Stats - Convert Essay to new DSL

Closes CNVS-13159

TEST PLAN
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Only code changes. Test plan would be the same as
https://gerrit.instructure.com/#/c/35096/

Change-Id: I0f26a3df1278d555237c803cebbe80cde1559065
Reviewed-on: https://gerrit.instructure.com/35097
Reviewed-by: Jason Madsen <jmadsen@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Ahmad Amireh <ahmad@instructure.com>