Easify read-only access to settings

This may or may not be done already as part of !49 (merged).

From !49 (comment 57372):

Yes, that should work at least. However for the access to settings we might want to think about other ways than reusing the view model that is mostly designed for the settings screen, including functions to update the settings. I fear we might need to use this viewModel() call then at several places where we actually only need to look up a single setting.

I'm not sure if that's the best way, but I would rather have a SettingsGateway or SettingsAdapter (feel free to come up with a better naming) that would be provided using CompositionLocalProvider as well. This class would only give read-access to the settings then.