Add simple miss chances for NPCs (#12978)

Doesn't consider juking potential but okay for now.

Content.Server/NPC/Systems/NPCCombatSystem.cs

@@ -1,9 +1,8 @@
 using Content.Server.Interaction;
 using Content.Server.Weapons.Ranged.Systems;
-using Content.Shared.CombatMode;
-using Content.Shared.Interaction;
 using Content.Shared.Weapons.Melee;
 using Robust.Shared.Map;
+using Robust.Shared.Random;
 using Robust.Shared.Timing;
 
 namespace Content.Server.NPC.Systems;
@@ -13,7 +12,9 @@ namespace Content.Server.NPC.Systems;
 /// </summary>
 public sealed partial class NPCCombatSystem : EntitySystem
 {
+    [Dependency] private readonly IGameTiming _timing = default!;
     [Dependency] private readonly IMapManager _mapManager = default!;
+    [Dependency] private readonly IRobustRandom _random = default!;
     [Dependency] private readonly GunSystem _gun = default!;
     [Dependency] private readonly InteractionSystem _interaction = default!;
     [Dependency] private readonly SharedAudioSystem _audio = default!;