feat(router): Allow redirect routes to use route names as target

[Tobbe]

When specifying a redirect route like <Route path="/simple" redirect="/newSimple" name="simple" /> the value of redirect is the path of the page the user should be redirected to. However, the paths can be long and annoying to type out. And if they ever change the redirect would now be broken.

Also, for private routes we do this:

<Router>
  <Route path="/" page={HomePage} name="home" />
  <PrivateSet unauthenticated="home">
    <Route path="/admin" page={AdminPage} name="admin" />
  </PrivateSet>
</Router>

Here, if a user isn't authenticated, the user will be redirected to the home route. Notice how the target route is specified by its name (home) instead of its path (/).

With this PR it's now also possible to redirect using the name of the target route, making our route behavior more consistent. So this will now work

<Router>
  <Route path="/" page={HomePage} name="home" />
  <Route path="/no-longer-exists" redirect="home" />
</Router>

Old style paths still works. The logic is super simple -> if the redirect value starts with / it's assumed to be a path. If not, it's assumed to be a route name. This should make this PR fully backwards compatible.