Redesigned LLM model selection in AI Assistant chat UI (now it's possible to search by filtering its name).

Redesigned UIDropDownList to inherit from UIDropDown which is a base class to handle different types of drop-downs. Added UIDropDownModelList which is the same as UIDropDownList but uses a UIListView by default so it's a model/view based DropDown.
Fix crash when changing states of the buttons in the build panel.
Increased the default animations speed.

src/examples/ui_dropdownmodellist/ui_dropdownmodellist.cpp

@@ -0,0 +1,51 @@
+#include <eepp/ee.hpp>
+#include <eepp/ui/models/itemlistmodel.hpp>
+#include <eepp/ui/uidropdownmodellist.hpp>
+
+using namespace EE::UI;
+using namespace EE::UI::Models;
+
+EE_MAIN_FUNC int main( int, char** ) {
+	UIApplication app( { 640, 480, "eepp - UIDropDownModelList Example" } );
+	app.getUI()->loadLayoutFromString( R"xml(
+			<LinearLayout layout_width="match_parent"
+						  layout_height="match_parent"
+						  orientation="vertical"
+						  padding="16dp">
+				<TextView layout_width="match_parent"
+						  layout_height="wrap_content"
+						  text="Model-Based Dropdown Example"
+						  margin_bottom="16dp" />
+
+				<DropDownModelList id="dropdown"
+								   layout_width="250dp"
+								   layout_height="wrap_content"
+								   pop-up-to-root="true"
+								   max-visible-items="4" />
+			</LinearLayout>
+	)xml" );
+
+	if ( !app.getWindow()->isOpen() )
+		return EXIT_FAILURE;
+
+	UIDropDownModelList* dropDown = app.getUI()->find<UIDropDownModelList>( "dropdown" );
+	if ( dropDown ) {
+		std::vector<std::string> options = { "Option 1: OpenGL",	  "Option 2: Vulkan",
+											 "Option 3: Direct3D 11", "Option 4: Direct3D 12",
+											 "Option 5: Metal",		  "Option 6: WebGL",
+											 "Option 7: Software" };
+
+		auto model = ItemListOwnerModel<std::string>::create( options );
+		dropDown->setModel( model );
+		dropDown->addEventListener( Event::OnItemSelected, []( const Event* event ) {
+			UIDropDownModelList* dropDown = event->getNode()->asType<UIDropDownModelList>();
+			ModelIndex index = dropDown->getListView()->getSelection().first();
+			if ( index.isValid() ) {
+				String text = dropDown->getListView()->getModel()->data( index ).toString();
+				Log::info( "Selected item index: %d, value: %s", (int)index.row(), text.c_str() );
+			}
+		} );
+	}
+
+	return app.run();
+}