operate_fallback!! shouldn't force the first argument to be copied

In this redirection:
https://github.com/jump-dev/MutableArithmetics.jl/blob/7344c9468072bd663feec7e4cdc1a0e98e34ea19/src/interface.jl#L592-L599
We redirect to `operate` because for instance, when it's used in the `@rewrite` macro, we want to modify the result so it cannot depend on the the arguments.
However, since the first argument was given to `operate!!`, it can actually be modified! So in this case, we want a result that does not depend on any argument **except** the first one.
This can causes performance issues in https://github.com/JuliaAlgebra/StarAlgebras.jl/pull/21/files#diff-3f191d1ba6c7bc538c1bf193064434a4984a0457baac3da62c9e6dede5d566aa for `canonical` as reported by @kalmarek