gh-105156: Deprecate the old Py_UNICODE type in C API (#105157)

Deprecate the old Py_UNICODE and PY_UNICODE_TYPE types in the C API:
use wchar_t instead.

Replace Py_UNICODE with wchar_t in multiple C files.

Co-authored-by: Inada Naoki <songofacandy@gmail.com>
9 files changed