Standards: teacher_scores query optimizations

[Erin007]

Querying for the progress tab is inefficient, particularly new queries for the standards tab related to TeacherScores. This causes performance problems, particularly for large sections. After issues were discovered in production, I temporarily stopped fetching standards data unless the standardsReport flag is on (#33467).

In this PR, to improve performance of the problematic queries :

• Extracted content fromget_level_scores_for_stage_for_student and then deleted it to move database hits to TeacherScores out of loops so we only hit that table once instead of on every iteration.
• Pass stage instead of stage.id as an argument to get_level_scores_for_stage_for_section so we don't have an additional database hit to re-fetch the stage.

I also added a test to ensure that increasing the number of students in a section doesn't increase the number of database hits and updated the TeacherScores model tests accordingly.