chore: Demonstrate use of hashmap with new result objects for analysis storage

[j-lanson]

This PR addresses the 4th task in #28 , showing how the new results.rs structs/enums can be used to replace AnalysisResults with a Hashmap<String, HCStoredResult>, enabling a future dynamic set of analyses to support the plugin architecture.

Particular focus on impl of struct AltAnalysisResults and the code savings of the following line:
let (act_score, outcome) = alt_results.table.get(ACTIVITY_PHASE).unwrap().score();

I also updated AnalysisResults::activity to be of type Option<HCStoredResults>. Since this makes it so the compiler cannot know the type is really ThresholdPredicate inside dyn HCPredicate, I had to do some Any wizardry and add as_any() as a trait func for HCPredicate so report_builder.rs could downcast it as such: let Some(pred) = analysis.as_any().downcast_ref::<ThresholdPredicate>(). This may be able to be removed in the future if new reporting infrastructure removes then need to access particular predicate fields.