Support optional loading of list analysis enrichment

Enrichment is automatically run for the results page, and is quite a heavy operation involving lots of HTTP requests. On slower computers, this causes a short freeze.

We should consider making it optional some way
- able to uncheck an *Always run* box in the enrichment column
- an *Analyze* button the user has to press to start enrichment (could also apply for all visualizations on the page)

*Update: We should set a threshold of 2000 to automatically run enrichment, and once exceeded, display a message explaining why enrichment isn't run, with a button to override it.*

Start at the results page and trace where enrichment is automatically triggered. Check how the enrichment column and visualizations initiate HTTP requests, then implement the stated 2000-result threshold, explanatory message, and override button. Done means large result sets avoid automatic enrichment while users can still explicitly start it.

Written by the indexing model from the issue text.