GeezerVison

This avoids overwriting the first few fields in the PyObject header with debug bytes (like 0xDD for dead bytes) in the free-threaded build. These fields may be accessed for a period after an object is deallocated.

For simplicity, this skips some of the filling of debug bytes for the "realloc" calls in the free-threaded build, because that case is more complex. The calls that delegate to mimalloc will be filled by mimalloc with debug bytes anyways.

• Issue: Keep ob_tid, ob_ref_local, and ob_ref_shared fields valid across allocations in free-threaded build #115491