feat(corelib): Extend trait

[julio4]

• Define the Extend trait: Extend a collection with the contents of an iterator.
• Implement ArrayExtend

Examples

let mut arr = array![1, 2, 3];
arr.extend((4..6_u32).into_iter());
assert_eq!(arr, array![1, 2, 3, 4, 5]);

Current Issue

Doing the trait bound on +IntoIterator<I> has the benefit of being able to pass any values that can be transformed in an Iterator, including Iterator themselves.
However it seems there's some inference issues:

let mut arr = array![1, 2];
arr.extend(array![3, 4, 5].into_iter());

Cause panic:

thread '<unnamed>' panicked at crates/cairo-lang-semantic/src/expr/inference.rs:1239:25:
assertion failed: impl_impl.impl_id().is_var_free(self.db)

Using +Iterator<I> works fine, but it's better to use IntoIterator here

[reviewable-StarkWare]

This change is