Test Data: Fixing endpoint not working #20044 (#20227)

* It worked before i must have broken it somehow. Commit as checkpoint

* Adding a reference from Web.UI.csproj to TestData to allow composers to be composed

* Changing readme and removing project reference

tests/Umbraco.TestData/LoadTestComposer.cs

@@ -8,5 +8,5 @@ namespace Umbraco.TestData;
 
 public class LoadTestComposer : IComposer
 {
-    public void Compose(IUmbracoBuilder builder) => builder.AddUmbracoTestData();
+    public void Compose(IUmbracoBuilder builder) => builder.AddUmbracoLoadTest();
 }