isListValuesAllEquals function
Returns true if list elements are all equals to value.
Implementation
bool isListValuesAllEquals(Object? list, [Object? eqValue]) {
  if (list == null || list is! List) return false;
  if (list.isEmpty) return false;
  eqValue ??= list.first;
  return listMatchesAll(list, (v) => v == eqValue);
}