[3.13] gh-71810: Fix corner case (length==0) for int.to_bytes() (GH-138739) (#138783)

[3.13] gh-71810: Fix corner case (length==0) for int.to_bytes() (GH-138739) (#138783)

gh-71810: Fix corner case (length==0) for int.to_bytes() (GH-138739)

```pycon
>>> (0).to_bytes(0, 'big', signed=True)
b''
>>> (-1).to_bytes(0, 'big', signed=True)  # was b''
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    (-1).to_bytes(0, 'big', signed=True)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
OverflowError: int too big to convert
```
(cherry picked from commit 011179a79a0d7b93ce074b25b0819e96b6dd3315)

Co-authored-by: Sergey B Kirpichev <skirpichev@gmail.com>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>