Move Access & AccessReader to shared. (#5798)

* git mv

* Move Access Component & system.

- Name space changes
- Rename AccessReader to AccessReaderComponent
- Also need an abstract TryGetSlot function for SharedInventoryComponent

* better TryGetSlot

* Ah yes, tests exist.

Content.Server/AI/Pathfinding/Accessible/AiReachableSystem.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using Content.Server.Access.Systems;
 using Content.Server.AI.Pathfinding.Pathfinders;
+using Content.Shared.Access.Systems;
 using Content.Shared.AI;
 using Content.Shared.GameTicking;
 using JetBrains.Annotations;