bpo-46008: Make runtime-global object/type lifecycle functions and state consistent. (gh-29998)

This change is strictly renames and moving code around.  It helps in the following ways:

* ensures type-related init functions focus strictly on one of the three aspects (state, objects, types)
* passes in PyInterpreterState * to all those functions, simplifying work on moving types/objects/state to the interpreter
* consistent naming conventions help make what's going on more clear
* keeping API related to a type in the corresponding header file makes it more obvious where to look for it

https://bugs.python.org/issue46008

Include/internal/pycore_genobject.h

@@ -0,0 +1,46 @@
+#ifndef Py_INTERNAL_GENOBJECT_H
+#define Py_INTERNAL_GENOBJECT_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
+
+/* runtime lifecycle */
+
+extern void _PyAsyncGen_Fini(PyInterpreterState *);
+
+
+/* other API */
+
+#ifndef WITH_FREELISTS
+// without freelists
+#  define _PyAsyncGen_MAXFREELIST 0
+#endif
+
+#ifndef _PyAsyncGen_MAXFREELIST
+#  define _PyAsyncGen_MAXFREELIST 80
+#endif
+
+struct _Py_async_gen_state {
+#if _PyAsyncGen_MAXFREELIST > 0
+    /* Freelists boost performance 6-10%; they also reduce memory
+       fragmentation, as _PyAsyncGenWrappedValue and PyAsyncGenASend
+       are short-living objects that are instantiated for every
+       __anext__() call. */
+    struct _PyAsyncGenWrappedValue* value_freelist[_PyAsyncGen_MAXFREELIST];
+    int value_numfree;
+
+    struct PyAsyncGenASend* asend_freelist[_PyAsyncGen_MAXFREELIST];
+    int asend_numfree;
+#endif
+};
+
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_INTERNAL_GENOBJECT_H */