pylifecycle.c: Multiple init/fini cleanup bugs

Bug report

Bug description:

Parent: https://github.com/python/cpython/issues/146102

https://gist.github.com/devdanzin/b022ff2d1304a4b2b8d3d8750abd8da5

pylifecycle.c: Multiple init/fini cleanup bugs

Summary

5 bugs in interpreter lifecycle:

1. new_interpreter (line 2534): return status bypasses switch-back after save_tstate detach → thread state corruption.
2. pycore_init_builtins (line 860): Direct return leaks bimod ref.
3. add_main_module (line 2762): bimod/loader refs leaked on PyDict_SetItemString failure.
4. finalize_clear_modules_dict (line 1685): Return value of PyObject_CallMethodNoArgs never DECREF'd.
5. init_sys_streams (line 3019-3031): Unchecked PySys_SetObject for stdin/stdout (stderr correctly checked).

CPython versions tested on:

CPython main branch, 3.15

Operating systems tested on:

No response

Linked PRs

• gh-149631

先從父 issue 和連結的 gist 開始，然後檢查 pylifecycle.c 中的 new_interpreter、pycore_init_builtins、add_main_module、finalize_clear_modules_dict 和 init_sys_streams。檢查每條回報的失敗路徑，並使用連結的 PR gh-149631 了解現有內容。完成標準是處理好全部五個 lifecycle 清理問題，同時不引入新的參照或 thread-state 問題。