Incorrect error message for ctypes bitfield overflow

[hyongtao-code]

Bug report

Bug description:

https://github.com/python/cpython/blob/main/Modules/_ctypes/cfield.c#L163-L164
The error message did not match the actual overflow check and omitted the bitfield size, making it misleading.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Windows

Linked PRs

• gh-143164: Fix incorrect error message for ctypes bitfield overflow #143165
• [3.14] gh-143164: Fix incorrect error message for ctypes bitfield overflow (GH-143165) #143176