Add new API Vector::insert and Vector::remove

[White-Green]

This PR adds insert and remove APIs to Vector.
closes: #95

Implementation

Previously, a Node could hold up to 1 << bits child Nodes. By extending the range of child Nodes to (i << bits) / 2..=1 << bits, we achieve faster insert and remove operations. This also makes it easier to implement Vector::{push_front, drop_first} (#17).

Regressions

Due to the uncertainty in the number of child elements in a Node, index calculations in methods like get have become more complex. As a result, Vector::get is approximately 3.5 times slower in benchmarks. Additionally, many white-box tests related to the Node structure have been rewritten.

[orium]

Hi. I'll take a look at this but it will take me some time to review, as I've been busy. Probably the end of next month.

[White-Green]

Thank you for taking the time. Please don't push yourself as I'm not in a hurry.