Established new Counter view for the Page content type

This view establishes a basic counter that increments on a per-path basis. This will simplify output caching for the new `[TopicResponseCache]` attribute (9bc5797). As part of this, updated the new `/Web/CachedPage` stub data (8cbf7da) to use this view.

Author: JeremyCaney

OnTopic.AspNetCore.Mvc.IntegrationTests.Host/Repositories/StubTopicRepository.cs

@@ -181,6 +181,9 @@ private static Topic CreateFakeData() {
       cacheProfile.Attributes.SetValue("Location", "Any");
 
       cachedPage.References.SetValue("CacheProfile", cacheProfile);
+      cachedPage.Attributes.SetValue("View", "Counter");
+
+      uncachedPage.Attributes.SetValue("View", "Counter");
 
       /*------------------------------------------------------------------------------------------------------------------------
       | Set to cache

OnTopic.AspNetCore.Mvc.IntegrationTests.Host/Views/Page/Counter.cshtml

@@ -0,0 +1,18 @@
+@getCounter()
+
+@functions {
+
+  //Establish a counter for each page path
+  public static Dictionary<string, int> pageCounter = new();
+
+  //Increment the counter for each call to a given page path
+  public int getCounter() {
+    var path = Context.Request.Path;
+    if (!pageCounter.ContainsKey(path)) {
+      pageCounter.Add(path, 0);
+    }
+    pageCounter[path] = pageCounter[path]+1;
+    return pageCounter[path];
+  }
+
+}