Issue #26588:

* _Py_HASHTABLE_ENTRY_DATA: change type from "char *" to "const void *"
* Add _Py_HASHTABLE_ENTRY_WRITE_PKEY() macro
* Rename _Py_HASHTABLE_ENTRY_WRITE_DATA() macro to
  _Py_HASHTABLE_ENTRY_WRITE_PDATA()
* Add _Py_HASHTABLE_ENTRY_WRITE_DATA() macro