Remove __unnest_placeholder from result projection on queries with struct unnest. #16894
Description
Is your feature request related to a problem or challenge?
As discussed in #16790, queries with struct unnest produce columns with a placeholder __unnest_placeholder, which looks a bit awkward and is difficult to use in queries.
It would be a good idea to try to remove it from result projection.
Describe the solution you'd like
No response
Describe alternatives you've considered
No response
Additional context
No response