Application activation does not work from toast for unpackaged app Framework 4.8

[11v1]

Describe the bug

If application is built for framework 4.8 then it's activation (when app is closed) from toast does not calls OnActivation after app start.

Steps to Reproduce

• [*] This can be reproduced in the Sample App. Need to change target framework to net48 and replace MainWindow.DownloadImageToDisk with:

  
  #if NET48
  using Windows.Web.Http;
  #endif        
  
      private static async Task<string> DownloadImageToDisk(string httpImage)
      {
          // Toasts can live for up to 3 days, so we cache images for up to 3 days.
          // Note that this is a very simple cache that doesn't account for space usage, so
          // this could easily consume a lot of space within the span of 3 days.
          try
          {
              if (ToastNotificationManagerCompat.CanUseHttpImages)
              {
                  return httpImage;
              }
  
              var directory = Directory.CreateDirectory(System.IO.Path.GetTempPath() + "WindowsNotifications.DesktopToasts.Images");
  
              if (!_hasPerformedCleanup)
              {
                  // First time we run, we'll perform cleanup of old images
                  _hasPerformedCleanup = true;
  
                  foreach (var d in directory.EnumerateDirectories())
                  {
                      if (d.CreationTimeUtc.Date < DateTime.UtcNow.Date.AddDays(-3))
                      {
                          d.Delete(true);
                      }
                  }
              }
  
              var dayDirectory = directory.CreateSubdirectory(DateTime.UtcNow.Day.ToString());
              string imagePath = dayDirectory.FullName + "\\" + (uint)httpImage.GetHashCode();
  
              if (File.Exists(imagePath))
              {
                  return imagePath;
              }

if NET48

            HttpClient c = new HttpClient();
            using (var stream = await c.GetInputStreamAsync(new Uri(httpImage)))
            {
                using (var fileStream = File.OpenWrite(imagePath))
                {
                    stream.AsStreamForRead().CopyTo(fileStream);
                }
            }

else

            HttpClient c = new HttpClient();
            using (var stream = await c.GetStreamAsync(httpImage))
            {
                using (var fileStream = File.OpenWrite(imagePath))
                {
                    stream.CopyTo(fileStream);
                }
            }

endif

            return imagePath;
        }
        catch
        {
            return string.Empty;
        }
    }

<!-- Being able to reproduce the problem in the sample app, really stream-lines the whole process in being able to discover, resolve, and validate bug fixes. -->

Steps to reproduce the behavior:

1. Change Microsoft.Toolkit.Win32.WpfCore.SampleApp target framework to net48
2. Paste above code to make project buildable
3. Start sample app
4. Press "Pop toast"
5. Close app
6. Press on notification to activate app
7. Application starts but event OnActivated is not called. System event log has entry that "DCOM server {...} was not activated for the allotted time"

When project is build for net core 3.1 then activation works as expected.

<!-- Provide as many code-snippets or XAML snippets where appropriate. -->

## Expected behavior
Application starts and OnActivated event is called.

<!-- A clear and concise description of what you expected to happen. -->

## Environment

<!-- Check one or more of the following options with "x" and replace the {build_number} and {minor_version} with the actual values -->

NuGet Package(s): Microsoft.Toolkit.Uwp.Notifications 7.1.1 <!-- Which NuGet Packages have you used -->

Windows 10 Build Number: 19043

Device form factor:

- [*] Desktop

Visual Studio version:

- [*] 2019 (16.11.3)

[ghost]

Hello 11v1, thank you for opening an issue with us!

I have automatically added a "needs triage" label to help get things started. Our team will analyze and investigate the issue, and escalate it to the relevant team if possible. Other community members may also look into the issue and provide feedback 🙌

[michael-hawker]

FYI @andrewleader