Move Tier 2 interpreter out of _PyEval_EvalFrameDefault

[gvanrossum]

See discussion starting here: faster-cpython/ideas#631 (comment)

Basically, we see no real perf improvement for having the two switches inside the same function, and we have some indication that on Windows the compiler is failing to optimize this giant function. In addition, the logic for each of the interpreters is somewhat complicated due to sharing variables and labels.

This is not as simple as reverting gh-111428 (issue gh-111520), but in the abstract, that's the proposal.

The priority isn't clear, but it's probably doing before the 3.13 feature freeze.

[gvanrossum]

This will probably be superseded by issue gh-118335 and its PR (gh-118339).

[gvanrossum]

This will probably be superseded by issue gh-118335 and its PR (gh-118339).

(Not really, when configured the Tier 2 interpreter will still co-habitate with the Tier 1 interpreter. But it's unclear if it matters, and we may dust it off later.)