[BUG] make static loop unrolling automatic, and warn if not possible

[daedalus5]

Bug Description

import warp as wp

RANGE = 5

@wp.kernel
def test_kernel:
    for i in range(wp.static(-RANGE), wp.static(RANGE)):
        ...

In the above example, -RANGE should be automatically statically evaluated. This will allow the loop to be unrolled, which makes kernels differentiable under certain conditions.