ULE trait should work on not just slices

[sffc]

This issue is intended to be discussed in the context of zerovec 1.0 / holistic design

I've thought this for a while but I wasn't able to find an issue for it. The trait is currently:

pub unsafe trait ULE
where
    Self: Sized + Copy + 'static,
{
    // Required method
    fn validate_byte_slice(bytes: &[u8]) -> Result<(), UleError>;

    // Provided methods
    fn parse_byte_slice(bytes: &[u8]) -> Result<&[Self], UleError> { ... }
    unsafe fn from_byte_slice_unchecked(bytes: &[u8]) -> &[Self] { ... }
    fn as_byte_slice(slice: &[Self]) -> &[u8] { ... }
}

I think we should add:

• validate_chunk(chunk: [u8; size_of::<Self>]) -> Result<(), UleError> (required method)
• parse_chunk (provided method)
• from_chunk_unchecked (provided method)

and then change validate_byte_slice to be a provided method.