len method
insert: Already implemented by list Returns the length of the Vec. Equivalent to length.
Implementation
// into_boxed_slice: will not implement, box is not a thing in dart
// into_flattened: Added as extension
// into_raw_parts: will not be implemented, not possible
// into_raw_parts_with_alloc: will not be implemented, not possible
// is_empty: Implemented by Iterable.isEmpty
// leak: will not be implemented, not possible
/// Returns the length of the Vec.
/// Equivalent to [length].
@pragma('vm:prefer-inline')
int len() => length;