[feature request] Vec::resize_with()

[tower120]

What title says.

[sgued]

Please describe in more details what this function would do

[tower120]

Same as resize(new_len, item), but resize_with(new_len, item_maker_fn).
For non-Clone items.

https://doc.rust-lang.org/std/vec/struct.Vec.html#method.resize_with