* Refactoring openssh_keypair for multiple backends
* Fixing cryptography backend validations
* Simplifying conditionals and excess variable assignments
* Fixing docs and adding cleanup for integration tests
* Fixing docs and public key validation bugs in crypto backend
* Enhancing cryptogagraphy utils to raise OpenSSHErrors when file not found
* Adding missed copyright and cleanup for idempotency test keys
* Fixing doc style
* Readding crypto/openssh for backwards compatibility
* Adding changelog fragment and final simplifications of conditional statements
* Applied initial review suggestions
* Integrating openssh module utils with openssh_keypair
* Added explicit PEM formatting for OpenSSH < 7.8
* Adding changelog fragment
* Adding OpenSSL/cryptography dependency for integration tests
* Adding private_key_format option and removing forced cryptography update for CI
* Fixed version check for bcrypt and key_format option name
* Setting no_log=False for private_key_format
* Docs correction and simplification of control flow for private_key_format
* Get rid of ansible.netcommon requirement by integrating module_utils/compat/ipaddress.py.
* Reorder imports.
* Update ignore.txt for plugins/module_utils/compat/ipaddress.py.
* Linting (flake8 / pep8).
* Remove accidentally commited test for ansible/ansible#66920.
