Improve WHERE handling to check the dimensions of full statements inside the condition, instead of just finding the first range object inside the statement.

[LonelyCat124]

PSyclone currently guesses the size of the WHERE loop by assessing the first range in the condition and assuming that is the dimension of the loop. This can lead to incorrect assessments in some cases, e.g. the WHERE statements found in this code fragment.

subroutine test
    real, allocatable, dimension(:) :: pivot, pivot2
    real :: min_pivot

    min_pivot = 1.0
    allocate(pivot(1:10000))

    WHERE(sum(pivot(:)) + pivot(1:5) < min_pivot) pivot(1:5) = min_pivot
    deallocate(pivot)
    end subroutine

We can be smarter now, and evaluate the size of SUM - this first case is wrong technically but we currently do something wrong and turn pivot(1:5) to just index over the full range.

Also this statement will be wrong due to #2722 but thats a separate problem.