copy/paste layer should keep Auxiliary Storage

[Michael-cd30]

Feature description

Because the Auxiliary Storage keeps information about labelling position, the copy/paste layer option should also copy and paste the auxiliary storage attached to the layer.

Additional context

It can be time consuming to manually place label on a large map. Therefore, this feature could save time.
Another option would be to add an "import auxiliary storage". With 3.20.1, only export is available.

[KVO-cartographer]

@gioman also it will be useful to add function "Save Labels as" to give ability to save the labels as an output layer containing text objects. (GeoPackage is the most suitable format for storing text object in QGIS, but not only GeoPackage should be available as an output format)

[threalslimtobeeee]

I created a Plugin named "Auxiliary Labeldata Importer". With it, the user can import auxiliary layers from other projects. It can only import auxiliary fields that are properties of the label placement. Maybe not anything you wish for, but a start :)

It is still flagged as experimental. I'd appreciate some testing and feedback.