PyTorch connector refractoring (#809)

* Pin torch==2.2.2 in CI to avoid a known error with 2.2.3

* Add SECURITY.md

* Update SECURITY.md

* Update SECURITY.md

* Correct typo in SECURITY.md

* Add Cornell papers

* Add Cornell papers

* Remove redundant text

* Update supported versions

* Update vulnerability statement

* Add 1.0 migration guide statement and light Readme restructuring

* Correct 1.0 migration guide statement

* Refractor torch_connector.py

* Add mypy ignores

* Add mypy ignores

* Spellcheck

* Revert to `_TorchNNFunction`

* Sanitize CI

Author: edoaltamura