CompetitionSerializer Simple vs Detail

[Didayolo]

@ mention of reviewers

@bbearce

Summary

Codabench is too slow to load. We need to speed up the public competitions page load speed.

I took the actual change from #1373, and removed the CircleCI problem fix which are already present in #1375.

Issue this PR resolves

• Performance problem - Pages are too slow to load #1327

A checklist for hand testing

• Use automation code from wiki (linked in issue 1327) to create lots of competitions
• Publish all challenges

docker compose exec django bash
python manage.py shell_plus
comps = Competition.objects.all()

for i in comps:
    i.published = True
    i.save()

• See if the page loads any faster

Checklist

• Code review by me
• Hand tested by me
• I'm proud of my work
• Code review by reviewer
• Hand tested by reviewer
• CircleCi tests are passing
• Ready to merge

[Didayolo]

Rebased develop to take into account the CircleCI fix