Add Clone trait for builtin

[FlammeShadow]

• Array::deep_clone is not appropriate #527
• FixedArray::deep_clone is NOT really a deep clone #1423

Different methods to clone a object like deep_clone, copy and clone have existed in the standard library. However, without Clone trait, we can't really implement a "deep_clone" method. I think we need a unified trait to clone various objects (like Rust's Clone).

[illusory0x0]

I think we also need copy trait

[FlammeShadow]

I think we also need copy trait

You mean a trait like Rust's Copy?

[illusory0x0]

I think we also need copy trait

You mean a trait like Rust's Copy?

element type is Immutable, we can use copy method rather than DFS or traverse data structure
this copy is Array::copy in moonbit.

impl[T : Clone] Clone for Array[T] with clone(self) {
  match T::mutability() {
    Mutable => self.map(T::clone)
    Immutable => self.copy()
  }
}

• add Clone trait #1438