feat: Implement int

[HarshitaKalani]

Towards: #492 and #3248

[HarshitaKalani]

I don't think we should be adding intrinsics for simple casts like this one. Cannot we simply insert a regular cast node here? -- #3691 (comment)

I implemented this using cast node but this has a problem as it does not handle arrays as elemental Intrinsics do. I think we will need to implement this as an intrinsic only, what say?

program main
    real(4) :: harvest(2) = [1, 2]
    print*, int(harvest)
end

$ lfortran a.f90
semantic error: Unexpected args, Int expects (int), (real) or (complex) as arguments
 --> a.f90:3:13
  |
3 |     print*, int(harvest)
  |             ^^^^^^^^^^^^ 


Note: Please report unclear, confusing or incorrect messages as bugs at
https://github.com/lfortran/lfortran/issues.
$ gfortran a.f90 && ./a.out
           1           2

[Pranavchiku]

I do not think we need IntegerConstructor, simply you can do Cast( <Type>toInt ) and this shall work.

program main
        real :: harvest
        harvest = 13.0
        print *, int(harvest)
end program

The changes in current PR do:

(IntegerConstructor
    (Cast
        (Var 2 harvest)
        RealToInteger
        (Integer 4)
        ()
    )
    (Integer 4)
    ()
)

We need to simply do:

(Cast
    (Var 2 harvest)
    RealToInteger
    (Integer 4)
    ()
)

This can be intrinsic_functions, just add a simple cast node and things will work.

[HarshitaKalani]

I think this is not the correct way, hence closing this. Continued in #3953