Better error message when an ARD is accidentally passed to `tbl_summary()`

[ddsjoberg]

This may apply to more of the tbl_*() functions as well. This could be generalized to a check that there are no list columns.

library(cards)

mtcars |> 
  ard_categorical(variables = cyl) |> 
  gtsummary::tbl_summary()
#> Error in sort.int(x, na.last = na.last, decreasing = decreasing, ...): 'x' must be atomic

^{Created on 2024-09-22 with reprex v2.1.1}