gh-69573: Check return value of msvcrt_putch and msvcrt_putwch - #155956

Description

This PR fixes a longstanding bug in the msvcrt module where the return values of the underlying Windows _putch and _putwch functions were ignored.

According to the Windows C Runtime documentation, these functions return EOF (or WEOF) when an error occurs (such as when the console is unattached or output is redirected improperly). Because the Python wrappers (msvcrt.putch and msvcrt.putwch) previously returned None unconditionally, these errors were silently swallowed.

Changes:

• Added a check for EOF in msvcrt_putch_impl.
• Added a check for WEOF in msvcrt_putwch_impl.
• If an error is detected, they now correctly raise an OSError via PyErr_SetFromErrno(PyExc_OSError).
• Added the corresponding NEWS blurb.

• Issue: msvcrt_putch/msvcrt_putwch don't check the return value of _putch/_putwch #69573