Quiz report should use user's preference of CSV

[Gao-Jun]

While generating quiz report, the generated CSV file doesn't use the user's preference of CSV. This patch fix this issue.

Test plan

• Update user preference of CSV, use semicolon(;) as separator.
• Create a new quiz, and have a submission. (quiz with no submission can not be exported)
• Export 'Student Analysis' or 'Item Analysis' of this quiz.

Expected
The exported CSV file should use semicolon(;) as separator

Actual result
The exported CSV file still use comma(,) as separator

[instructure-sentry-integration]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: app/models/quizzes/quiz_statistics.rb

Function	Unhandled Issue
generate_csv	InstFS::ServiceError: received code "502" from service, with message " Quizzes::Quiz... Event Count: 2
generate_csv	InstFS::BadRequestError: received code "400" from service, with message ""The service received no request body and has tim... ... Event Count: 1

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[Gao-Jun]

How to view the detail of these 'Unhandled Issue'?