[fix][math] Fix error in Division of Array and a Scalar

[shivasankarka]

Error description

fn main() raises:
    var list: List[Scalar[nm.f64]] = List[Scalar[nm.f64]]()
    for i in range(200):
        list.append(Scalar[nm.f64](1e-5))

    var array = nm.array[nm.f64](list).reshape(nm.Shape(200, 1))
    var den = nm.exp(-array) + 1.0
    var result = Scalar[nm.f64](1.0) / (den)
    print("r: ", r)

The above code produces an array filled with 2.0 which is wrong since the expected result is an array filled with 0.5. This error occurred due to the symmetric implementation of all arithmetic operators i.e array +-*/ scalar, but this results in wrong value for division since it always calculates array / scalar even when the user input is (scalar / array).

Solution

This PR fixes this error by adding a new function to the backends that calculate the array and scalar arithmetic operations so that array / scalar and scalar / array result in the correct values.

[forfudan]

I somehow got confused about the backends and how arithmetic operations are finally down to the backend functions in _math_funcs.mojo. Perhaps we need to write a small API guidance for this part.

[shivasankarka]

@forfudan you are right, I also kinda got confused when I was fixing this.