Improved assignment list loading time

[david-yz-liu]

Proposed Changes

(Describe your changes here. Also describe the motivation for your changes: what problem do they solve, or how do they improve the application or codebase? If this pull request fixes an open issue, use a keyword to link this pull request to the issue.)

This PR improves the loading time of the assignments index route for instructors, building on the work of #7787.

In particular, I introduced a new Assignment.batch_stats method, which calls Assignment.batch_instructor_stats (new) or Assignment.batch_ta_stats (existing). I also introduced a new Assignment.current_results batch method, which generalizes the existing Assignment#current_results to return the current results from multiple assignments.

Screenshots of your changes (if applicable)

Associated documentation repository pull request (if applicable)

Type of Change

(Write an X or a brief description next to the type or types that best describe your changes.)

Type	Applies?
🚨 Breaking change (fix or feature that would cause existing functionality to change)
✨ New feature (non-breaking change that adds functionality)
🐛 Bug fix (non-breaking change that fixes an issue)
🎨 User interface change (change to user interface; provide screenshots)
♻️ Refactoring (internal change to codebase, without changing functionality)	X
🚦 Test update (change that only adds or modifies tests)
📦 Dependency update (change that updates a dependency)
🔧 Internal (change that only affects developers or continuous integration)

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[coveralls]

Pull Request Test Coverage Report for Build 23124412654

Details

• 59 of 59 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 91.68%

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Totals
Change from base Build 23091690132:	0.005%
Covered Lines:	45108
Relevant Lines:	48388

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💛 - Coveralls