547 hotfix mightee

[Lukas113]

closes #547

This PR addresses the following:

• Reading correct cols from .fits files of MIGHTEE and GLEAM
• Implemented a correct and generalized version to read sky-sources from .fits file. The previous version had the following issues:
  • Didn't consider unit-scaling & checks
  • Didn't allow to read frequencies
  • Was not generalized
• Introduced helper-classes with tests to address these issues

[codecov]

Codecov Report

Attention: Patch coverage is 94.07666% with 17 lines in your changes are missing coverage. Please review.

Project coverage is 66.86%. Comparing base (9e2b77c) to head (ef59de9).

Files	Patch %	Lines
karabo/simulation/sky_model.py	94.03%	17 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #560      +/-   ##
==========================================
+ Coverage   65.96%   66.86%   +0.89%     
==========================================
  Files          49       49              
  Lines        4792     4970     +178     
==========================================
+ Hits         3161     3323     +162     
- Misses       1631     1647      +16     

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[mpluess]

Looks good as far as I can tell