Python 3.11 and return (un)suppressed findings

[mlflr]

This PR has 2 changes:

• Migrate to Python 3.11 since 3.8 will be EOL
• Instead of returning a boolean showing success/failure returns a tuple returning the same boolean and a list of (un)suppressed findings
  • Unit Tests now verify results using the output instead of arguments of mocked calls

Note: the library works on 3.12, but Prospector (linter) does not. There are PRs open to fix those issues, but the main maintainer is not responding and other collaborators don't want to approve them due to lack of knowledge...