Internal helper that prints a short, human-readable description of a
procr_table object to the console: its subtable names, dimensions, the data
matrices it contains, the currently active layout, and which metadata slots
are populated.
Details
Multi-subtable objects (length(tab$subtable) > 1L) are not yet
supported and will raise an error, matching the same limitation in
print.procr_table() and to_gt().