Refactor frozen table columns

[matthew-white]

See getodk/central-frontend#811 (comment). We have frozen columns in a few tables, but right now they involve a fair amount of complexity: see the TableFreeze component.

In terms of the user experience, I think there are accessibility concerns with the current implementation. The TableFreeze component renders two <table> elements, which I think would be difficult to navigate using a screen reader.

The linked comment suggests a couple of possible solutions.

[matthew-white]

This comment suggests a solution if only the first column needs to be frozen: getodk/central-frontend#160 (comment)