Internal sanity check for symmetrise() and related operations that
require reciprocity. Reciprocity is only defined when each grouping has
the same levels on the participant and contact side, which lets us flatten
the rank-2K array into a square T x T matrix.
check_part_cnt_dims_match(matrix, k, op)invisibly NULL on success; otherwise raises a cli error
the rank-2K contact matrix
the number of groupings (length(dim(matrix)) %/% 2L)
short label used in the error message