This MR adds the code which displays cycle analytics on a group level.
It reuses the cycle_analytics_bundle file which will later be removed.

This feature is currently behind the analytics feature flag.

Add a simple haml_lint linter to report all plain nodes.
"Plain nodes" in HAML are scritpless plaintext leaf nodes.

Add haml-lint_todo to onboard new haml linters.
Excludes existing NoPlainNodes lints.