Introduce a `isa_wrapped_array` function

Most details are in https://github.com/EnzymeAD/Reactant.jl/pull/369#issuecomment-2541402690. I will copy over the important parts.

We introduce a function isa_wrapped_array that downstream packages can use to mark that their array type wraps another array. Using a union type from Adapt doesn't solve this problem, because that fundamentally doesn't extend to new array types.

With this function, we can override functions inside our custom interpreter. Consider this simple example of extending LinearAlgebra.diag

Base.Experimental.@overlay REACTANT_METHOD_TABLE function LinearAlgebra.diag(
    x::AbstractArray{T,2}, k::Integer=0
) where {T}
    if isa_wrapped_array(x) && ancestor(x) isa TracedRArray
        y = materialize_traced_array(x) # convert it to a known type
        return diag(y, k)
    else
        # invoke diag(x) on NativeInterpreter
    end
end

Start with the details in PR 369's issue comment, especially the proposed isa_wrapped_array behavior and the LinearAlgebra.diag overlay example. Determine the interface needed for downstream array types and how it supports the custom interpreter use case. Done means the function is introduced with behavior matching that specification and the relevant usage is covered.