Make the 'purge' operation show an interactive popup by default, with
a preview of the type and amount of data-blocks to be deleted.
Idea and initial UI/UX design are from @Harley (see PR !117242).
Add a new `BKE_lib_query_unused_ids_amounts` to query expected amounts
of deleted IDs. This function does not tag IDs in main anymore.
Factorize most parameters (and output data) into a new struct
`LibQueryUnusedIDsData`.
Part of PR #117304.