Add column counts as default, independently from table showing it

rtables result data frames do not report column N’s. These numbers are available from the TableTree object but may not be straightforward to retrieve. This is NOT considered as a critical feature to have, because whenever a frequency is calculated, n and % are often (if not always) reported in the rtables result data frame, and column N could then be calculated (i.e. if n and % are correct, N should be correct). However, it would be nice to explore ways to get this column N into the result data frame of rtables

Start by tracing how the TableTree object stores column N values and how those values are converted into the rtables result data frame. Done means the result data frame reports column counts independently of whether the table displays them, with existing frequency-derived n and % behavior preserved.