Added ``Py_BEGIN_CRITICAL_SECTION_SEQUENCE_FAST`` and
``Py_END_CRITICAL_SECTION_SEQUENCE_FAST`` macros to make it possible to use
PySequence_Fast APIs safely when free-threaded, and update str.join to work
without the GIL using them.
Added ``Py_BEGIN_CRITICAL_SECTION_SEQUENCE_FAST`` and
``Py_END_CRITICAL_SECTION_SEQUENCE_FAST`` macros to make it possible to use
PySequence_Fast APIs safely when free-threaded, and update str.join to work
without the GIL using them.