Feat: nightly preview test run

[kneerose]

List of changes

• Add a schedule to run nightly tests on the preview for both integration and backend tests
• Skip the proposal submission test for the schedule workflow trigger
• Remove the old report only if the report history is more than 10
• Append nightly- for the report name when the workflow is triggered by schedule
• Add new report name on new line

Checklist

• related issue
• My changes generate no new warnings
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the changelog
• I have added tests that prove my fix is effective or that my feature works

[github-actions]

✅ All checks succeeded

[github-actions]

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[github-actions]

✅ All checks succeeded

[github-actions]

✅ All checks succeeded

[github-actions]

✅ All checks succeeded

[github-actions]

✅ All checks succeeded