Source-compatible export and conversion workflows

[anna-teruel]

Part of #993

This issue focuses on implementing export/save functionality for:

• corrected tracked datasets after manual refinement
• dataset conversion workflows between supported tracking software

Motivation

movement already provides conversion/export utilities such as: to_dlc_style_df, to_dlc_file, to_lp_file etc. But these conversions are not supported in the current GUI.

We plant o implement a save/export widget (#997).

Currently, movement datasets are converted into napari-compatible layers for visualization. To support the export conversion, we additionally need to add functionality to:

1. convert napari layer state back into movement xarray.Dataset.
2. use the implemented functions to save datasets into a target source format.

Proposed functionality

Implement functionality to convert napari layer state back into valid movement dataset and then integrate this with existing movement export utilities, depending on the selected target software. This issue should integrate with the planned "Save tracked data" widget (#997).

I think the synchronization and conversion to xarray.Datasets should happen only on save. Do you agree?