Respect excluded locations in forecast report

[mschulz-asphericon]

Is your feature request related to a problem?
Having a separate available qty, that isn't respected in the forecase could be misleading.

Describe the solution you'd like
The excluded locations should also be respected in the forecast. So the on hand amount should rather use the available qty.

Additional context
This could also affect the moves that are shown by the forecast report, depending on which locations to consider. We had already prepared a similar approach by adding a boolean "is_available_quantity" to stock.location and trying to consider it in the forecast, but we are running into problems when adjusting the "_get_domain_locations_new" to respect it. Either quantities are not respected correctly for orderpoints, or the forecasted qty is just incorrect.