Implement Box, Rc and Arc blanket trait impls for all rs-matter pub traits

[ivmarkov]

While rs-matter is no_std and no-alloc, the user app might not be and might be using the allocator.

Therefore, it might be useful to have (behind a #[cfg(feature = "alloc")]) blanket trait impls of all our public traits for the alloc types:

• impl<T> MyTrait for Box<T> where T: MyTrait { ... } - this for all traits
• impl<T> MyTrait for Rc<T> where T: MyTrait { ... } - this for traits which have only &self methods
• impl<T> MyTrait for Arc<T> where T: MyTrait { ... } - this for traits which have only &self methods; needs to additionally be protected to only execute on targets that do have core::sync::atomic
• impl<T> MyTrait for portable_atomic::Arc<T> where T: MyTrait { ... } - this for traits which have only &self methods; and only if we decide to keep the portable-atomic dependency around; perhaps behind a #[cfg(feature = "portable-atomic")]