[BUG] Traits with functions not defined in the namespace where @derive is called

[mtfishman]

The following kind of pattern doesn't work right now:

module MyArrays
struct MyArray{T,N,A<:AbstractArray{T,N}} <: AbstractArray{T,N}
  parent::A
end

using Derive: Derive
using LinearAlgebra: LinearAlgebra
function Derive.derive(::Val{:Mul}, type)
  return quote
    LinearAlgebra.mul!(::Any, ::$type, ::$type, ::Number, ::Number)
  end
end
end

@derive MyArrays.MyArray MyArrays.Mul

We should be able to make it work with judicious use of GlobalRef in @derive, see for example https://github.com/ITensor/Derive.jl/blob/f97d55a21109e0390bb542237da532aec9d3ce0c/src/interface_macro.jl#L36.

This will allow us to include these functions in the AbstractArrayOps trait: https://github.com/ITensor/Derive.jl/blob/f97d55a21109e0390bb542237da532aec9d3ce0c/src/traits.jl#L18-L19.