Change SymIntNode into an intrusive pointer (#82548)
This will make the pointer type a single word, which is important
for packing it into an int64_t
This time, this diff doesn't segfault when you build with DEBUG mode; more details at https://github.com/pybind/pybind11/issues/4099
Signed-off-by: Edward Z. Yang <ezyangfb.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/82548
Approved by: https://github.com/albanD
