Allowing dynamic expressions for "openByDefault"

### Description

I would like to be able to use **dynamic expressions** in connection with "openByDefault" in RepeatingGroups. When one has a rather complicated table-in-table it is a good idea to only show the outer table before opening anything. If there is only one row, i would like the single outer row to be open from the start.

### Additional Information

_No response_

Start by locating the RepeatingGroups implementation and the handling of openByDefault in the TypeScript frontend. Check how dynamic expressions are represented elsewhere, then verify that a single outer row can open initially while nested tables remain closed; the issue provides no test or file names to run.

Written by the indexing model from the issue text.