Implement Serialize for [T; L]

[DasLixou]

implement Serialize for a x-long array.
something like impl<T: Serialize, const L: usize> Serialize for [T; L] { .. }
with that its possible to do:

#[derive(Serialize)]
pub struct MyStruct<const R: usize> {
    pub rows: [PosSpan; R],
}

[Max-Meldrum]

See https://github.com/est31/serde-big-array

[uuhan]

See https://github.com/est31/serde-big-array

If serde is used in bindgen, it is not easy to add serde-big-array to long array field.

[hrxi]

Looks like a duplicate of #1937.