`DataValidationView` (the `Build a Submission` view) Refactor 8 - The actual `DataValidationView` refactor

[hepcat72]

Summary Change Description

Refactored the DataValidationView to use StudyLoader instead of call_command("load_study", ...).

Affected Issues/Pull Requests

• Partially addresses #829
• Merges into PR #1025
• Next PR: #1016

Review Notes

See comments in-line.

Checklist

This pull request will be merged once the following requirements are met. The author and/or reviewers should uncheck any unmet requirements:

• Review requirements
  • Minimum approvals: 1
  • No changes requested
  • All blocking issues resolved by reviewers
  • Specific reviewers: @add_username_here
  • Review period: 2 days
• Associated issue/pull request requirements:
  • [x] All requirements in affected issues marked "resolved" are satisfied
  • [x] All required pull requests are merged (or none)
• Basic requirements
  • [x] All linters pass
  • [x] All tests pass
  • [x] All conflicts resolved
• Overhead requirements
  • [x] New/changed method tests implemented/updated (or no change)
  • [ ] Updated Unreleased section of changelog.md (or no change)
  • [x] Migrations created & committed (or no change)