Make table structure consistent

[asizemore]

We return data for four tables so far:

1. The variable coverage table
2. mosaic stats table
3. box plot stats table
4. R^2 table in scatter

Ideally these would all have the same structure so that the front end can use a generic VizStatsTable component. May only be able to standardize 2-4 but still.

To Dos

• [ ] Look at each example of how we use table and figure out what data is needed (on front end, too) for each
• [ ] Create standardized response
• [ ] Create/implement new component in web-eda (see https://github.com/VEuPathDB/web-eda/issues/1253)