Update MainPage UI

[dansiegel]

What would you like to be added:

Currently we have a basic navigation layout with optional content for MauiEmbedding... This should be updated to support the following 3 scenarios:

1. -http true -server true -maui false -nav regions
   • Show Navigation UI for basic understanding of how Navigation works
   • Show basic Weather Forecast UI with pull to refresh. Initialize with existing IWeatherCache
2. -http false -maui false -nav regions
   • Show the Navigation UI for basic understanding of how Navigation works
   • Show basic counter UI similar to issue Update Blank app MainPage  #490. Update the MainViewModel / MainModel for the counter
3. -http true -server true -maui true -nav regions
   • Show Navigation UI for basic understanding of how Navigation works
   • Show basic Weather Forecast UI with pull to refresh. Initialize with existing IWeatherCache
   • Show Maui EmbeddedControl with Counter.

[DevTKSS]

would be great to have the server-http thing as templated design in the generated app