Fixed size arrays

[ArielElp]

Introducing the fixed size array type to the language:

let arr1: [u64; 5] = [1,2,3,4,5];
let arr2: Span<u64> = [1,2,3,4,5].span();

In addition, we'll have the capability of defining const fixed size array, which are analogous to dw in CairoZero:

const arr: [u64; 5] = [1,2,3,4,5];

To pass the const value cheaply between functions (without copying), you should pass box as follows:

fn get_arr(arr: Box<[u64; 5]>) { ... }

get_arr(BoxTrait::new(arr));

[ArielElp]

closed by #5145, #5147, #5184