Filtering reagents (#18211)

* Making it work

* Refactoring

* Autoformat revert

* Implementing suggestions

* Changed to file scoped namespaces.

Content.Client/Guidebook/Controls/ISearchableControl.cs

@@ -0,0 +1,9 @@
+namespace Content.Client.Guidebook.Controls;
+public interface ISearchableControl
+{
+    public bool CheckMatchesSearch(string query);
+    /// <summary>
+    ///    Sets the hidden state for the control. In simple cases this could just disable/hide it, but you may want more complex behavior for some elements.
+    /// </summary>
+    public void SetHiddenState(bool state, string query);
+}