Update CI to reasonable versions and fix resulting issues

Our current CI config is too old to support collections. The version of ansible-lint we used is several major versions and significant changes behind.

For now, just use a plain Alpine Linux image and install the required software on the fly (it’s fast enough) and consider whether to build a custom image at another time.

.ansible-lint

-parseable: true
-quiet: true
+---
 use_default_rules: true
-skip_list:
-  - '204'  # line length is checked by yamllint
-  - '401'  # git checkout must contain explicit version
-  - '701'  # 7xx is about ansible galaxy guidelines
-  - '702'
-  - '703'