Refactor core sorting function

[fjorka]

Description

Currently, the detected cores in the TMA are assigned numbers based on their position in a row and column (using the rounded position of the left upper corner).
This approach fails when:

• Cores are not evenly distributed within a TMA
• The entire array is skew

The function should be rewritten using a more robust approach to handle uneven or skewed layouts.

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Acceptance criteria / Done when

• A new version of the multiplex_pipeline.roi_utils.sort_cores function is implemented
• Unit tests are written to validate the new function against uneven and skewed TMA layouts