Array: separate out uses of broadcast iter, unify fail message
Array: separate out uses of broadcast iter, unify fail message

The code size cost was pretty big for expanding a fail!() in each
arithmetic operation impl. bench_std_add performance does actually increase by
10% with this change.

SuperFluffy/rust-ndarray,SuperFluffy/rust-ndarray,Pireax/rust-ndarray,Pireax/rust-ndarray