Incorrect MRO cache entry is populated for types that do not have a version assigned

Bug report

Bug description:

_PyType_LookupRefAndVersion will populate the incorrect cache entry if it is called with a type that does not have a version tag (tp_version_tag is 0). I think this only impacts performance, not correctness. The next call to _PyType_LookupRefAndVersion for the same (type, name) pair will miss the cache, but will populate the correct entry, so any subsequent calls will hit the cache. Additionally, this may create some amount of unnecessary thrash on the cache.

The root of the issue is that the version tag is an input to the hash that is used to determine the cache entry and we do not recompute the hash, and the associated cache entry, after assigning a version.

_PyType_LookupRefAndVersion first computes the cache entry:

https://github.com/python/cpython/blob/39e69a7cd54d44c9061db89bb15c460d30fba7a6/Objects/typeobject.c#L5542-L5544

If the cache entry doesn't match, and a type version was assigned successfully, it populates the same entry:

https://github.com/python/cpython/blob/39e69a7cd54d44c9061db89bb15c460d30fba7a6/Objects/typeobject.c#L5629-L5634

The next call for the same (type, name) pair, will find a different entry, because the type version is used to compute the hash that indexes into the cache:

https://github.com/python/cpython/blob/39e69a7cd54d44c9061db89bb15c460d30fba7a6/Objects/typeobject.c#L46-L48

It looks like the change to use the same entry was introduced in gh-113930. cc @DinoV

CPython versions tested on:

3.13, 3.14

Operating systems tested on:

Linux

從 Objects/typeobject.c 中的 _PyType_LookupRefAndVersion 以及所引用行附近的快取雜湊計算開始。追蹤無版本路徑和新指派版本路徑，然後確認重複查找使用的是依指派版本索引的快取項目，而不是留下不必要的項目。適當的回歸檢查應展示修正後的快取行為，同時不改變查找結果。