Improves examine code

Examining now has larger range. Ghosts have no range limit.
Fixed some messy code and some bad netcode.

Content.Shared/GameObjects/Components/Mobs/ExaminerComponent.cs

@@ -0,0 +1,30 @@
+using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization;
+using Robust.Shared.ViewVariables;
+
+namespace Content.Shared.GameObjects.Components.Mobs
+{
+    /// <summary>
+    ///     Component required for a player to be able to examine things.
+    /// </summary>
+    public sealed class ExaminerComponent : Component
+    {
+        public override string Name => "Examiner";
+
+        [ViewVariables(VVAccess.ReadWrite)]
+        private bool _doRangeCheck = true;
+
+        /// <summary>
+        ///     Whether to do a distance check on examine.
+        ///     If false, the user can theoretically examine from infinitely far away.
+        /// </summary>
+        public bool DoRangeCheck => _doRangeCheck;
+
+        public override void ExposeData(ObjectSerializer serializer)
+        {
+            base.ExposeData(serializer);
+
+            serializer.DataField(ref _doRangeCheck, "DoRangeCheck", true);
+        }
+    }
+}

Content.Shared/GameObjects/EntitySystems/ExamineSystemShared.cs

@@ -0,0 +1,35 @@
+using Content.Shared.GameObjects.Components.Mobs;
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects.Systems;
+using Robust.Shared.Interfaces.GameObjects;
+
+namespace Content.Shared.GameObjects.EntitySystems
+{
+    public abstract class ExamineSystemShared : EntitySystem
+    {
+        public const float ExamineRange = 8f;
+        public const float ExamineRangeSquared = ExamineRange * ExamineRange;
+
+        [Pure]
+        protected static bool CanExamine(IEntity examiner, IEntity examined)
+        {
+            if (!examiner.TryGetComponent(out ExaminerComponent examinerComponent))
+            {
+                return false;
+            }
+
+            if (!examinerComponent.DoRangeCheck)
+            {
+                return true;
+            }
+
+            if (examiner.Transform.MapID != examined.Transform.MapID)
+            {
+                return false;
+            }
+
+            var delta = examined.Transform.WorldPosition - examiner.Transform.WorldPosition;
+            return delta.LengthSquared <= ExamineRangeSquared;
+        }
+    }
+}