refactor: unify runtime sets, update naming of event channels (#17)

Some general refactors:
Turns HeroPartySO into a runtime set class.
Make runtime set an IEnumerable
Simplify name of events

Reviewed-on: #17
Reviewed-by: zephyr <zephyr@noreply.localhost>
Co-authored-by: Michael <mep053@gmail.com>
Co-committed-by: Michael <mep053@gmail.com>

Assets/TestsPlaymode/HeroPartyTest.cs

@@ -1,5 +1,4 @@
 using System.Collections;
-using System.Collections.Generic;
 using NUnit.Framework;
 using UnityEditor;
 using UnityEngine;
@@ -18,6 +17,6 @@ public class HeroPartyTest
         Assert.AreEqual(1, hero.party.Count);
         Object.Destroy(instance);
         yield return null;
-        Assert.IsEmpty(hero.party.UnitList);
+        Assert.IsEmpty(hero.party);
     }
 }