gh-100288: Specialise LOAD_ATTR_METHOD for managed dictionaries

[Fidget-Spinner]

• Issue: Finish up LOAD_ATTR specialisation #100288

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @Fidget-Spinner for commit 576c914 🤖

If you want to schedule another build, you need to add the :hammer: test-with-buildbots label again.

[markshannon]

The stats show only a small increase in specialization effectiveness, and that the new instruction has a 40% miss rate.

I think we would be better off trying to reduce the number of objects with dictionaries than specializing for that case.

[Fidget-Spinner]

Hmm yes hit rate only went from 82.0% to 82.5%. This isn't worthwhile.