Update MVC template to use new Problem helpers in error handler

[DamianEdwards]

Relies on #8537

Update error handler action method to use new problem helper method #8537:

[Route("/error")]
public ActionResult<ProblemDetails> HandleError([FromHeader] string accept)
{
    if (accept.Contains("text/html"))
    {
        return View("Error", new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
    }
 
    return Problem();
}

[mkArtakMSFT]

Moving this to a future milestone so that we can address this after we'll finalize the templates.

[ryanbrandenburg]

Blocked by #8537.

[pranavkm]

This should be unblocked now.

[mkArtakMSFT]

Moving this to 5.0 after a discussion with @glennc and @pranavkm.

[mkArtakMSFT]

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.