Py_TRASHCAN_SAFE_BEGIN and Py_TRASHCAN_SAFE_END are deprecated since Python 3.11
and result in a deprecation warning when building against Python 3.11.

This follows the suggested migration to Py_TRASHCAN_BEGIN and Py_TRASHCAN_END
in https://docs.python.org/3/whatsnew/3.11.html

Py_TRASHCAN_BEGIN only exists since Python 3.8, while we still support 3.7,
so also use the suggested macro to support older Python versions.