feat: implement Encode, Decode, Type for `Arc<str>` and `Arc<[u8]>` (and `Rc` equivalents)

[joeydewaal]

fixes #1904

Implements Encode, Decode for Arc<str>, Arc<[u8]>, Rc<str> and Rc<[u8]>.

Edit: this depends on #3674 now because of the blanket impl's for Type.