Option to import all devices regardless of their groups

[FreshlyBrewedCode]

Is your feature request related to a problem? Please describe. A new option introduced in v1.2.0 allows the user to select which groups should be imported. The integration will only import devices that are in any of the selected groups. This behaviour will cause devices that are not assigned to a group to never be imported.

Describe the solution you'd like Add an option to import all devices regardless of what groups are selected.

Describe alternatives you've considered Move all devices to at least one group.

Additional context The option should be added to the get_data_schema function in config_flow.py and get_imported_nodes in helpers.py should return all nodes if the option is enabled.