Admin Tool: Observe entities in an extra viewport (#36969)

* camera

* add console command

* change verb name to camera

* placeholder text

* add button to player panel

* orks are indeed the best

* visibility flag fix

* not a datafield

* more follower fixes

* more cleanup

* add zooming

* resizing real

* remove commented out code

* remove AddForceSend

* comment

* Use OS window and add some comments

* fix comments and variable name

* Needs RT update

* Minor grammarchange

* Fix warning

* Cleanup

* almost working...

* fix bug

* oswindow update

* Remove need for RequestClosed.

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Co-authored-by: beck-thompson <beck314159@hotmail.com>
Co-authored-by: PJB3005 <pieterjan.briers+git@gmail.com>

Content.Shared/Eye/VisibilityFlags.cs

@@ -6,9 +6,10 @@ namespace Content.Shared.Eye
     [FlagsFor(typeof(VisibilityMaskLayer))]
     public enum VisibilityFlags : int
     {
-        None   = 0,
+        None = 0,
         Normal = 1 << 0,
-        Ghost  = 1 << 1,
-        Subfloor = 1 << 2,
+        Ghost = 1 << 1, // Observers and revenants.
+        Subfloor = 1 << 2, // Pipes, disposal chutes, cables etc. while hidden under tiles. Can be revealed with a t-ray.
+        Admin = 1 << 3, // Reserved for admins in stealth mode and admin tools.
     }
 }