The sum of two Array{T, 0}s should be an Array{T, 0}

[bzinberg]

Minimal example:

julia> fill(1) + fill(2)
3

This causes pathologies such as

julia> fill(1) + fill(2) + fill(3)
6

julia> (fill(1) + fill(2)) + fill(3)
ERROR: MethodError: no method matching +(::Int64, ::Array{Int64,0})

(In my opinion it should be possible to add an Int64 to an Array{Int64, 0}, but that's a separate issue.)

[mbauman]

Thanks for the reminder. This is a dup of #28866, but this prompted me to propose a fix for it in #32122.