Table: Frozen columns for nested table

Currently, frozen columns are disable for nested tables because they act a bit unpredictably. We should land on a solid idea for how they should work and then implement that, and remove that restriction. - we want to look to inspiration in [AG Table](https://ag-grid.com/javascript-data-grid/column-pinning/). Their docs don't seem to demonstrate that particular combo, but we should be able to set one up to see what they do. - one thing we think may be good would be to freeze the nested parent row at the top of the screen, so that the content of the frozen columns can be compared with the nested children.