Centralise all the type checking

[stevan]

There is a ton of type checking spread around all the BUILD methods, they include error messages and other silliness. We can consolidate all these into a Type::Tiny library and then just use that. Should cut down on a lot of duplication, not to mention improve the type checking we currently have.

[stevan]

As mentioned in #15, it is probably a good idea to centralize all this into Graph::QL::Util::Assertions and have that use the Type::Tiny library internally perhaps, or maybe just use Ref::Util directly for most stuff, but support folks using Type::Tiny types as well.

This needs some thinking 🤔