Avoid emptying and recreating all UI cards on every update (#21990)

By making the UI elements persistent, it allows tooltips to remain
on-screen when other elements are updated - in particular, the number
of research points, which is updated regularly.

Co-authored-by: Eoin Mcloughlin <helloworld@eoinrul.es>

Content.Client/Research/UI/MiniTechnologyCardControl.xaml.cs

@@ -1,4 +1,4 @@
-using Content.Shared.Research.Prototypes;
+using Content.Shared.Research.Prototypes;
 using Robust.Client.AutoGenerated;
 using Robust.Client.GameObjects;
 using Robust.Client.UserInterface;
@@ -12,6 +12,9 @@ namespace Content.Client.Research.UI;
 [GenerateTypedNameReferences]
 public sealed partial class MiniTechnologyCardControl : Control
 {
+    /// The technology that this control represents
+    public readonly TechnologyPrototype Technology;
+
     public MiniTechnologyCardControl(TechnologyPrototype technology, IPrototypeManager prototypeManager, SpriteSystem spriteSys, FormattedMessage description)
     {
         RobustXamlLoader.Load(this);
@@ -24,5 +27,6 @@ public sealed partial class MiniTechnologyCardControl : Control
         var tooltip = new Tooltip();
         tooltip.SetMessage(description);
         Main.TooltipSupplier = _ => tooltip;
+        Technology = technology;
     }
 }