gh-132775: Add _PyCode_GetScriptXIData() (gh-133480)

This converts functions, code, str, bytes, bytearray, and memoryview objects to PyCodeObject,
and ensure that the object looks like a script.  That means no args, no return, and no closure.
_PyCode_GetPureScriptXIData() takes it a step further and ensures there are no globals.

We also add _PyObject_SupportedAsScript() to the internal C-API.