2.7.0: Unit.set_ports(), and minor docs, CI, and test improvements

This release includes one new feature, a new function Unit.set_ports() to declare which ports should be open. We recommend using this method rather than managing multiple Unit.open_port() and Unit.close_port() calls:

• feat: add Unit.set_ports() for declarative port opening #1005

We've also made a few small improvements to the documentation:

• docs: reduce the amount of detail in the open/close port methods in #1006
• docs: remove 'you' and 'your' from docstrings in #1003
• docs: minor cleanup of the HACKING doc in #1016

Finally, we've also made a start expanding our type hinting to cover the test suite, and made a couple of minor improvements/fixes to our CI:

• test: add type hints to the test_infra tests in #1008
• test: add type hints to test_log tests by in #1009
• test: fix type hinting on test_jujuversion tests in #1011
• test: fix type hint warnings in test_private tests in #1012
• test: add type hinting to test_lib by in #1012
• test: add type hinting to test_helpers in #1014
• ci: use Go 1.20 for real Pebble tests in #1004
• ci: re-enable integration tests with mysql-*operator by in #1013

(Thanks @tonyandrewmeyer for your first contributions, and welcome to the team!)

Full Changelog: 2.6.0...2.7.0