Backport PyType_Modified on keys version change to 3.15

Summary:
<!-- pyimport-metadata:begin -->
This diff adds a patch to the `third-party/python/3.15` Meta-internal fork.

Call PyType_Modified when the shared dictionary keys change

Reviewed By: itamaro

Differential Revision: D108322589

fbshipit-source-id: d8692cff1022150e45c641a7be6d05916eadea40

Author: DinoV

Include/internal/pycore_dict.h

@@ -90,6 +90,8 @@ typedef struct {
 } PyDictUnicodeEntry;
 
 extern PyDictKeysObject *_PyDict_NewKeysForClass(PyHeapTypeObject *);
+extern void _PyDict_RemoveKeysForClass(PyHeapTypeObject *);
+extern void _PyDict_SplitKeysInvalidated(PyDictKeysObject* keys);
 extern PyObject *_PyDict_FromKeys(PyObject *, PyObject *, PyObject *);
 
 /* Implementations of the `|` and `|=` operators for dict, used by the
@@ -239,6 +241,17 @@ struct _dictkeysobject {
        see the DK_ENTRIES() / DK_UNICODE_ENTRIES() functions below */
 };
 
+struct _instancekeysobject {
+    PyTypeObject* dsk_owning_type;
+    struct _dictkeysobject dsk_keys;
+};
+
+static inline struct _instancekeysobject *_PyDictKeys_AsSharedKeys(struct _dictkeysobject *keys)
+{
+    assert(keys->dk_kind == DICT_KEYS_SPLIT);
+    return _Py_CONTAINER_OF(keys, struct _instancekeysobject, dsk_keys);
+}
+
 /* This must be no more than 250, for the prefix size to fit in one byte. */
 #define SHARED_KEYS_MAX_SIZE 30
 #define NEXT_LOG2_SHARED_KEYS_MAX_SIZE 6