feat: set integer size for FTorch FT_INT

Integer size for FTorch can now be controlled using parameter `FT_INT`.

Currently, the default is set to `int32` but this could be changed if
required.

This fixes an issue on windows with the latest version of ifx/ifort
which builds with a different integer type leading to the following
error:

```
error #6284: There is no matching specific function for this generic function reference.   [TORCH_TENSOR_FROM_ARRAY]
   in_tensors(1) = torch_tensor_from_array(in_data, tensor_layout, torch_kCPU)
-------------------^
```

examples/1_SimpleNet/simplenet_infer_fortran.f90

@@ -21,7 +21,7 @@ program inference
    real(wp), dimension(5), target :: in_data
    real(wp), dimension(5), target :: out_data
    real(wp), dimension(5), target :: expected
-   integer :: tensor_layout(1) = [1]
+   integer(FT_INT) :: tensor_layout(1) = [1]
 
    ! Set up Torch data structures
    ! The net, a vector of input tensors (in this case we only have one), and the output tensor

examples/2_ResNet18/resnet_infer_fortran.f90

@@ -33,10 +33,10 @@ subroutine main()
 
       integer, parameter :: in_dims = 4
       integer :: in_shape(in_dims) = [1, 3, 224, 224]
-      integer :: in_layout(in_dims) = [1, 2, 3, 4]
+      integer(FT_INT) :: in_layout(in_dims) = [1, 2, 3, 4]
       integer, parameter :: out_dims = 2
       integer :: out_shape(out_dims) = [1, 1000]
-      integer :: out_layout(out_dims) = [1, 2]
+      integer(FT_INT) :: out_layout(out_dims) = [1, 2]
 
       ! Path to input data
       character(len=100) :: data_dir

examples/4_MultiIO/multiionet_infer_fortran.f90

@@ -23,7 +23,7 @@ program inference
    real(wp), dimension(4), target :: out_data1
    real(wp), dimension(4), target :: out_data2
    real(wp), dimension(4) :: expected
-   integer :: tensor_layout(1) = [1]
+   integer(FT_INT) :: tensor_layout(1) = [1]
 
    ! Set up Torch data structures
    ! The net, a vector of input tensors (in this case we only have one), and the output tensor