Use IOC to de-couple FlatdeviceChooserVM from FlatdeviceVM

What is the purpose of this Pull Request?

• de-couple device chooser VM from device VM

• get rid of _wrongPrivateFieldNotation

• move to fluent assertions

How were the changes tested?

• all relevant unit tests pass - there are a fe in Flatwizard and ImageMetadata that are not passing, same as in the develop branch

Are there relevant Issues in the tracker that this PR will fix?

Screenshots

Notes