Fix framerate dependent UI animations

Robust.Client/UserInterface/Controls/ScrollBar.cs

@@ -74,7 +74,7 @@ namespace Robust.Client.UserInterface.Controls
             else
             {
                 _updating = true;
-                Value = MathHelper.Lerp(Value, ValueTarget, Math.Min(args.DeltaSeconds * 15, 1));
+                Value = UIAnimations.LerpAnimate(Value, ValueTarget, args.DeltaSeconds, 15);
                 _updating = false;
             }
         }

Robust.Client/UserInterface/CustomControls/DropDownDebugConsole.xaml.cs

@@ -71,7 +71,7 @@ namespace Robust.Client.UserInterface.CustomControls
             }
             else
             {
-                _curAnchorOffset = MathHelper.Lerp(_curAnchorOffset, targetOffset, args.DeltaSeconds * 20);
+                _curAnchorOffset = UIAnimations.LerpAnimate(_curAnchorOffset, targetOffset, args.DeltaSeconds, 20);
             }
 
             UpdateAnchorOffset();

Robust.Client/UserInterface/UIAnimations.cs

@@ -0,0 +1,13 @@
+using System;
+using Robust.Shared.Maths;
+
+namespace Robust.Client.UserInterface;
+
+internal static class UIAnimations
+{
+    // From https://blog.pkh.me/p/41-fixing-the-iterative-damping-interpolation-in-video-games.html
+    public static float LerpAnimate(float a, float b, float dt, float rate)
+    {
+        return MathHelper.Lerp(a, b, 1f - MathF.Exp(-dt * rate));
+    }
+}