gh-117045: Add code object to function version cache (#117028)

Changes to the function version cache:

- In addition to the function object, also store the code object,
  and allow the latter to be retrieved even if the function has been evicted.
- Stop assigning new function versions after a critical attribute (e.g. `__code__`)
  has been modified; the version is permanently reset to zero in this case.
- Changes to `__annotations__` are no longer considered critical. (This fixes gh-109998.)

Changes to the Tier 2 optimization machinery:

- If we cannot map a function version to a function, but it is still mapped to a code object,
  we continue projecting the trace.
  The operand of the `_PUSH_FRAME` and `_POP_FRAME` opcodes can be either NULL,
  a function object, or a code object with the lowest bit set.

This allows us to trace through code that calls an ephemeral function,
i.e., a function that may not be alive when we are constructing the executor,
e.g. a generator expression or certain nested functions.
We will lose globals removal inside such functions,
but we can still do other peephole operations
(and even possibly [call inlining](https://github.com/python/cpython/pull/116290),
if we decide to do it), which only need the code object.
As before, if we cannot retrieve the code object from the cache, we stop projecting.

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