Cleanup Objective files, add PickSpecificPersonComponent (#35802)

* cleanup objectives

* remove unrelated access restriction

* review

Content.Server/Objectives/Components/PickRandomHeadComponent.cs

@@ -1,12 +1,8 @@
-using Content.Server.Objectives.Systems;
-
 namespace Content.Server.Objectives.Components;
 
 /// <summary>
 /// Sets the target for <see cref="TargetObjectiveComponent"/> to a random head.
 /// If there are no heads it will fallback to any person.
 /// </summary>
-[RegisterComponent, Access(typeof(KillPersonConditionSystem))]
-public sealed partial class PickRandomHeadComponent : Component
-{
-}
+[RegisterComponent]
+public sealed partial class PickRandomHeadComponent : Component;