insertRowAt method
Insert value near visible index (clamped). With a filter active the
row lands next to the corresponding master row.
Implementation
void insertRowAt(int index, T value) => _structural(() {
final master = (index >= 0 && index < _viewMaster.length) ? _viewMaster[index] : _all.length;
_all.insert(master.clamp(0, _all.length), value);
});