Vt parallise source detection

[kenfus]

• Adds parallized source detection
• Adds functionality to split a karabo.image into multiple parts
• Adds mosaicking for source detection plots
• General improvements of the karabo image class

[codecov[bot]]

Codecov Report

Attention: 44 lines in your changes are missing coverage. Please review.

Comparison is base (f1e3cc2) 72.91% compared to head (94b8fa9) 74.96%.

Files	Patch %	Lines
karabo/sourcedetection/result.py	75.00%	39 Missing :warning:
karabo/imaging/image.py	96.34%	3 Missing :warning:
karabo/util/dask.py	33.33%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #523 +/- ## ========================================== + Coverage 72.91% 74.96% +2.04% ========================================== Files 35 35 Lines 3652 3859 +207 ========================================== + Hits 2663 2893 +230 + Misses 989 966 -23 ```

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[kenfus]

Overall nice changes.

Before merging, please address the requested changes.

Done! Please have another look.

[kenfus]

@Lukas113 Please have another look. I would like to later restructure source detection completely, see #528