Function canonical_results_filter_key 

pub fn canonical_results_filter_key(raw: &str) -> String

What: Normalize a results_filter label for map keys and settings.conf suffixes.

Inputs:

• raw: Value from repos.conf (may contain -, spaces, etc.).

Output:

• Lowercase string with non-alphanumeric runs folded to a single _.

Details:

• Matches results_filter_show_<token> in settings.conf where token uses the same rule.