gh-89653: PEP 670: unicodeobject.h uses _Py_CAST() (GH-92696) (GH-92703)

gh-89653: PEP 670: unicodeobject.h uses _Py_CAST() (GH-92696) (GH-92703)

Use _Py_CAST() and _Py_STATIC_CAST() in macros wrapping static inline
functions of unicodeobject.h.

Change also the kind type from unsigned int to int: same parameter
type than PyUnicode_FromKindAndData().

The limited API version 3.11 no longer casts arguments to expected
types.
(cherry picked from commit d0c9353a79c2003385c83892db5dfd4e443474c9)

Co-authored-by: Victor Stinner <vstinner@python.org>
Co-authored-by: Victor Stinner <vstinner@python.org>