Add get_group_name to expose SSL_get0_group_name (#1442)

* Add get_group_name to expose SSL_get0_group_name

* Update test with consistent ordering

* Add decorator for the get group guard flag

* ruff format

* Skip test if not Cryptography_HAS_SSL_GET0_GROUP_NAME

* Add test case for if group returns NULL

* Fix test - add guard to check for session

* Set cryptography min to 46.0.0

* Drop Python 3.7 support

* Reflect in CHANGELOG.rst that Python 3.7 has been dropped

* Add comment about guard against segfault