HandsSystem Refactor (#38438)

* checkpoint

* pt 2

* pt... i forgot

* pt 4

* patch

* More test fixes

* optimization!!!

* the REAL hand system

* fix RetractableItemActionSystem.cs oversight

* the review

* test

* remove test usage of body prototype

* Update Content.IntegrationTests/Tests/Interaction/InteractionTest.cs

Co-authored-by: Tayrtahn <tayrtahn@gmail.com>

* hellcode

* hellcode 2

* Minor cleanup

* test

* Chasing the last of the bugs

* changes

---------

Co-authored-by: Tayrtahn <tayrtahn@gmail.com>

Content.Shared/Stacks/SharedStackSystem.cs

@@ -146,7 +146,7 @@ namespace Content.Shared.Stacks
             }
 
             // This is shit code until hands get fixed and give an easy way to enumerate over items, starting with the currently active item.
-            foreach (var held in Hands.EnumerateHeld(user, hands))
+            foreach (var held in Hands.EnumerateHeld((user, hands)))
             {
                 TryMergeStacks(item, held, out _, donorStack: itemStack);