Cleanup gun containers (probably last time) (#8575)

- snake_case instead of kebab-case
- Remove old MagazineBarrel containers
- Remove old event

Content.Shared/Weapons/Ranged/Events/MagazineAutoEjectEvent.cs

@@ -1,13 +0,0 @@
-using Robust.Shared.Serialization;
-
-namespace Content.Shared.Weapons.Ranged.Events
-{
-    /// <summary>
-    /// This is sent if the MagazineBarrel AutoEjects the magazine
-    /// </summary>
-    [Serializable, NetSerializable]
-    public sealed class MagazineAutoEjectEvent : EntityEventArgs
-    {
-        public EntityUid Uid;
-    }
-}

Content.Shared/Weapons/Ranged/Systems/SharedGunSystem.ChamberMagazine.cs

@@ -11,7 +11,7 @@ namespace Content.Shared.Weapons.Ranged.Systems;
 
 public abstract partial class SharedGunSystem
 {
-    protected const string ChamberSlot = "gun-chamber";
+    protected const string ChamberSlot = "gun_chamber";
 
     protected virtual void InitializeChamberMagazine()
     {

Content.Shared/Weapons/Ranged/Systems/SharedGunSystem.Magazine.cs

@@ -10,7 +10,7 @@ namespace Content.Shared.Weapons.Ranged.Systems;
 
 public abstract partial class SharedGunSystem
 {
-    protected const string MagazineSlot = "gun-magazine";
+    protected const string MagazineSlot = "gun_magazine";
 
     protected virtual void InitializeMagazine()
     {