Unify "fallback" pages - check for titles only.

Author: ilonatommy

src/Components/test/E2ETest/ServerRenderingTests/NoInteractivityTest.cs

@@ -70,8 +70,7 @@ public void CanUseServerAuthenticationStateByDefault()
     public void CanRenderNotFoundPageAfterStreamingStarted()
     {
         Navigate($"{ServerPathBase}/streaming-set-not-found");
-        Browser.WaitForElementToBeVisible(By.Id("test-info"));
-        Browser.Equal("Default Not Found Page", () => Browser.Exists(By.Id("test-info")).Text);
+        Browser.Equal("Default Not Found Page", () => Browser.Title);
     }
 
     [Theory]

src/Components/test/E2ETest/ServerRenderingTests/StatusCodePagesTest.cs

@@ -30,12 +30,13 @@ public void StatusCodePagesWithReExecution(bool setNotFound, bool streaming)
         string streamingPath = streaming ? "streaming-" : "";
         Navigate($"{ServerPathBase}/reexecution/{streamingPath}set-not-found?shouldSet={setNotFound}");
 
-        string expectedTitle = setNotFound ? "Re-executed page" : "Original page";
-        Browser.Equal(expectedTitle, () => Browser.Title);
-        var infoText = Browser.FindElement(By.Id("test-info")).Text;
         // streaming when response started does not re-execute
-        string expectedInfoText = streaming ? "Default Not Found Page" : setNotFound ? "Welcome On Page Re-executed After Not Found Event" : "Any content";
-        Assert.Contains(expectedInfoText, infoText);
+        string expectedTitle = streaming
+            ? "Default Not Found Page"
+            : setNotFound
+                ? "Re-executed page"
+                : "Original page";
+        Browser.Equal(expectedTitle, () => Browser.Title);
     }
 
 }

src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/NotFoundPage.razor

@@ -1,5 +1,6 @@
 @page "/not-found"
 
-<h3 id="test-info">Default Not Found Page</h3>
-<p>This page is used for a workaround of NavigationManager.NotFound() method, used in SSR when the response already started and changing it to 404 is not possible.
+<PageTitle>Default Not Found Page</PageTitle>
+
+<p id="test-info">This page is used for a workaround of NavigationManager.NotFound() method, used in SSR when the response already started and changing it to 404 is not possible.
     This workaround triggers navigation to a constant "not-found" relative path.</p>