[Draft][Fori_loop|While_loop] Lower torch.while_loop with python dispatch for simple addition

[ManfeiBai]

Due to torch.while_loop is defined in torch/_higher_order_ops/while_loop.py, not described in native_functions.yaml, lower torch.while_loop via python dispatch like PR#5763

this is the source PR for all other PRs

other PRs: https://github.com/pytorch/xla/pull/6532, https://github.com/pytorch/xla/pull/6529