N+1 query problem on dashboards

[mathjazz]

The new stats code (#3536) is making a separate DB query for each of the 369 locales in the /teams page to get theirs stats, which makes it noticeably slower than the old code.

We should change the way get_chart() works and only do 1 query for all locales.

[eemeli]

As noted in #3546 (review):

We're still hitting the N+1 problem in:

• ajax_projects()
• ajax_teams()
• ajax_resources()

[mathjazz]

This might be related. The spikes happen when collect_insights runs.