Remove deprecated static analysis

[RobbeSneyders]

This PR removes a bunch of deprecated static analysis config files:

• The Catwatch repository has been archived
• The Codevalidator repository has been archived
• Coverage: Python 2 support has been dropped and the remaining Python 3 config is the same as the default config
• No idea which tool relies on .checkignore, but it doesn't seem to break anything
• @hjacobs can you confirm that it's ok to remove the Zappr config?

We should also change the default branch to main on codeclimate. @jmcs is this something you can do?

[coveralls]

Coverage decreased (-0.007%) to 97.138% when pulling 1df5bc0 on remove-deprecated-static-analysis into f46551c on main.

[hjacobs]

👍