gh-123091: Use more _Py_IsImmortalLoose()

[encukou]

Switch more _Py_IsImmortal(...) assertions to _Py_IsImmortalLoose(...), to account for stable-ABI extensions changing the refcount of immortal objects (similar to the _Py_IMMORTAL_BIT/_Py_IMMORTAL_REFCNT design that was approved in PEP-683 but never implemented).

The remaining calls to _Py_IsImmortal are in free-threaded-only code, initialization of core objects, tests, and guards that fall back to code that works with mortal objects.

• Issue: Stable ABI: Objects/bytesobject.c:122: PyBytes_FromStringAndSize: Assertion '_Py_IsImmortal(op)' failed. #123091

[vstinner]

The remaining calls to _Py_IsImmortal are in free-threaded-only code, initialization of core objects, tests, and guards that fall back to code that works with mortal objects.

Remaining calls:

$gitgrep'assert.*Py_IsImmortal'|grep-vLooseInclude/internal/pycore_stackref.h: assert(_Py_IsImmortal(obj)); Modules/_testcapi/immortal.c: assert(_Py_IsImmortal(object)); Objects/codeobject.c: assert(_Py_IsImmortal(entry->value)); Objects/object.c: assert(!_Py_IsImmortal(op)); Objects/object.c: assert(_Py_IsImmortal(constants[i])); Objects/structseq.c: assert(_Py_IsImmortal(type)); Objects/typeobject.c: assert(_Py_IsImmortal((PyObject*)self)); Objects/unicodeobject.c: assert(!_Py_IsImmortal(s)); Programs/_testembed.c: assert(_Py_IsImmortal(str1)); Python/crossinterp.c: assert(_Py_IsImmortal((PyObject*)type)); Python/crossinterp.c: assert(_Py_IsImmortal((PyObject*)info->builtin)); Python/optimizer_symbols.c: assert(_Py_IsImmortal(val_42)); Python/optimizer_symbols.c: assert(_Py_IsImmortal(val_43));

[vstinner]

LGTM. IMO it should be backported to 3.13.

[miss-islington-app]

Thanks @encukou for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @encukou, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 57c471a6880956338549380fc5fb35c986937901 3.13 

[bedevere-app]

GH-123622 is a backport of this pull request to the 3.13 branch.