gh-91731: Replace Py_BUILD_ASSERT() with static_assert() (#91730)

Python 3.11 now uses C11 standard which adds static_assert()
to <assert.h>.

* In pytime.c, replace Py_BUILD_ASSERT() with preprocessor checks on
  SIZEOF_TIME_T with #error.
* On macOS, py_mach_timebase_info() now accepts timebase members with
  the same size than _PyTime_t.
* py_get_monotonic_clock() now saturates GetTickCount64() to
  _PyTime_MAX: GetTickCount64() is unsigned, whereas _PyTime_t is
  signed.

Python/fileutils.c

@@ -956,7 +956,7 @@ static wchar_t *
 _Py_ConvertWCharForm(const wchar_t *source, Py_ssize_t size,
                      const char *tocode, const char *fromcode)
 {
-    Py_BUILD_ASSERT(sizeof(wchar_t) == 4);
+    static_assert(sizeof(wchar_t) == 4, "wchar_t must be 32-bit");
 
     /* Ensure we won't overflow the size. */
     if (size > (PY_SSIZE_T_MAX / (Py_ssize_t)sizeof(wchar_t))) {