SkyModel Class: Accept OSKAR and RASCIL backends

[lmachadopolettivalle]

Implement changes described in https://github.com/i4Ds/Karabo-Pipeline/issues/421 for the SkyModel Class.

After a design discussion on 08.02.2024 with @Lukas113 and @kenfus we decided on the following approach:

• Continue storing source catalog data in a 2D numpy array, inspired by the OSKAR data format
• Introduce a method in SkyModel to export sources as a list of RASCIL SkyComponents, which can then be used to compute visibilities and later dirty images
• Create tests for the conversion to RASCIL format

This design choice allows users to benefit from existing code in Karabo to load, filter and visualize SkyModel instances, while also allowing for RASCIL-specific interferometry later in the pipeline.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 85.45455% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 66.03%. Comparing base (e0517ae) to head (400bec4). Report is 4 commits behind head on main.

Files	Patch %	Lines
karabo/simulation/sky_model.py	82.05%	7 Missing :warning:
karabo/simulation/line_emission.py	80.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #544 +/- ## ========================================== + Coverage 65.76% 66.03% +0.27% ========================================== Files 47 49 +2 Lines 4504 4796 +292 ========================================== + Hits 2962 3167 +205 - Misses 1542 1629 +87 ```

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