gh-130373: Avoid locking in _LOAD_ATTR_WITH_HINT

[DinoV]

Adds a lock-free lookup of the hinted location

https://github.com/facebookexperimental/free-threading-benchmarking/tree/main/results/bm-20250219-3.14.0a5+-6a1fe7e-NOGIL

• Issue: _LOAD_ATTR_WITH_HINT should be able to work lock-free in the free-threaded builds #130373

[colesbury]

I think we should de-opt here if the condition doesn't hold. The critical section is escaping so previously validated guards might not hold.

Something like:

EXIT_IF(!_Py_IsOwnedByCurrentThread((PyObject *)dict_o) && !IS_DICT_SHARED(dict_o));

EDIT: EXIT_IF instead of DEOPT_IF

[DinoV]

I think we need to do DEOPT_IF because apparently we can't mix and match them. I've updated it to do the ownership check and then mark the dictionary as shared when doing the specialization.

[mpage]

@DinoV - this lgtm modulo Sam's comment. Can you take a look?

[mpage]

LGTM. The tail calling check failure should go away if you merge main. Not sure about the other failing check.

[mpage]

LGTM