bpo-44590: Lazily allocate frame objects (GH-27077)

* Convert "specials" array to InterpreterFrame struct, adding f_lasti, f_state and other non-debug FrameObject fields to it.

* Refactor, calls pushing the call to the interpreter upward toward _PyEval_Vector.

* Compute f_back when on thread stack, only filling in value when frame object outlives stack invocation.

* Move ownership of InterpreterFrame in generator from frame object to generator object.

* Do not create frame objects for Python calls.

* Do not create frame objects for generators.