Macro vortex_array::impl_encoding

macro_rules! impl_encoding {
    ($id:literal, $code:expr, $Name:ident) => { ... };
}

Macro to generate all the necessary code for a new type of array encoding. Including:

1. New Array type that implements AsRef<ArrayData>, GetArrayMetadata, ToArray, IntoArray, and multiple useful From/TryFrom implementations.
2. New Encoding type that implements ArrayEncoding.
3. New metadata type that implements ArrayMetadata.