gh-139165: Make Py_SIZE, Py_IS_TYPE,Py_ SET_SIZE regular functions in stable ABI (GH-139166)

* Make Py_{SIZE,IS_TYPE,SET_SIZE} regular functions in stable ABI

Group them together with Py_TYPE & Py_SET_TYPE to cut down
on repetitive preprocessor macros.
Format repetitive definitions in object.c more concisely.

Py_SET_TYPE is still left out of the Limited API.