bpo-44525: Specialize calls to normal python classes

[markshannon]

Specializes calls to "normal" Python classes. That is, classes that inherit from object or other "normal" classes and do not override __new__.

The specialized form creates the object (self) pushes a shim frame to replace the result of __init__ with self and jumps into __init__.

Provides a ~1% speedup

https://bugs.python.org/issue44525

[markshannon]

This needs one or two additional checks that the __init__ function's code object is of the correct form.

[markshannon]

I'm closing this in favor of a two part specialization approach. See faster-cpython/ideas#210