gh-150942: Speed up BytesIO.readlines() using reference-stealing append (#155171)

* gh-150942: Use reference-stealing append in BytesIO.readlines

* gh-150942: Add NEWS entry for BytesIO.readlines optimization

* gh-150942: Fix NEWS cross-reference

* gh-150942: Simplify BytesIO.readlines NEWS entry

Author: Taeknology

Misc/NEWS.d/next/Library/2026-08-04-19-50-52.gh-issue-150942.B8ytes.rst

@@ -0,0 +1,2 @@
+Improve the performance of :meth:`~io.IOBase.readlines` for
+:class:`io.BytesIO`.

Modules/_io/bytesio.c

@@ -1,6 +1,7 @@
 #include "Python.h"
 #include "pycore_bytesobject.h"       // _PyBytes_ResizeKeepOnError()
 #include "pycore_critical_section.h"  // Py_BEGIN_CRITICAL_SECTION()
+#include "pycore_list.h"              // _PyList_AppendTakeRef()
 #include "pycore_object.h"
 #include "pycore_pyatomic_ft_wrappers.h"
 #include "pycore_sysmodule.h"         // _PySys_GetSizeOf()
@@ -664,11 +665,9 @@ _io_BytesIO_readlines_impl(bytesio *self, PyObject *arg)
         line = PyBytes_FromStringAndSize(output, n);
         if (!line)
             goto on_error;
-        if (PyList_Append(result, line) == -1) {
-            Py_DECREF(line);
+        if (_PyList_AppendTakeRef((PyListObject *)result, line) < 0) {
             goto on_error;
         }
-        Py_DECREF(line);
         size += n;
         if (maxsize > 0 && size >= maxsize)
             break;