Returns the total element count of a vector (array) column named
name, read from an open parquet_reader (reader), across every row
(i.e. nrows * col_size) in total_elements, dispatched by its
integer(int32)/integer(int64) kind. Reads no column data for a scalar or FIXED_SIZE_LIST
column (nrows and col_size are both already known from the file footer/schema), so this is
safe to call even on a column whose total element count itself exceeds int32 -- unlike an
earlier implementation, which materialized the whole column just to answer this query and
could hit Arrow's own int32 list-index ceiling on a large enough column (see CLAUDE.md's
"Guarding a hard Arrow int32-only ceiling"). A plain LIST/LARGE_LIST column has no
schema-level width, so it is measured one row group at a time by the same helper
parquet_get_col_size uses -- data is read, but never more than one row group at once.