Implement STORE_ATTR specialization "family" for PEP 659 adaptive interpreter

[markshannon]

STORE_ATTR has a couple of worthwhile specializations:

• Attrribute is in instance dictionary
• Attribute is a slot

There may be others, but those two will be good to be going on with.

[markshannon]

Implementation: https://github.com/faster-cpython/cpython/tree/specialize-store-attr
Results are underwhelming: https://gist.github.com/markshannon/29e31e1acb51abdcacb0935144d1fc61

I suspect the overhead of maintaining ordering and the version number, combined with the inefficiency of handling both split key and combined dictionaries is mostly cancelling out the advantage of specialization.

The specialization of LOAD_ATTR also suffers from the inefficiency of two types of dictionaries.
So I'm putting this on hold until we have investigated better object and dictionary layout, which will benefit both LOAD_ATTR and STORE_ATTR.

[markshannon]

python/cpython#27590