Fixes gh-15325

Unlike the others, PyInt_Check has a special meaning distinc from PyLong_Check, so only the places where the difference doesn't matter have been updated here.

We no longer need to use the compatibility function after dropping
support for Python 2.7. In some cases unicode was the correct string
type rather than the bytes of the compatibility version and bugs in the
array `__complex__` and array `__array_interface__` methods have been
fixed by changing that.

In https://github.com/python/cpython/pull/20290 CPython changed
`Py_TYPE` from a macro to an inline function.  This requires a code
change to us `Py_SET_TYPE` instead when using `Py_TYPE()` as a lvalue
in c code.

In https://github.com/python/cpython/pull/20429 CPython changed
`Py_SIZE` from a macro to an inline function.  This requires a code
change to us `Py_SET_SIZE` instead of using `Py_SIZE` as a lvalue in c
code.

Dropping the support for python 2, the difference in module setup do not have to be accounted
for anymore. This removes the macros and ifdef's related to module setup code and python 2
support.

Note that the extension module dict seems to be never dereferenced
(there is an additional reference to it kept around somewhere).
This reference seems to part of the C python module loading
(possibly intentionally), and I could not find how to remove it or
where it originates from.