test(mc): Add integration test for Retina-GKE, refactor test dir

[SRodi]

Description

• add integration test for Retina on GKE
• add package utils and refactor test directory

Related Issue

#1267

Checklist

• I have read the contributing documentation.
• I signed and signed-off the commits (git commit -S -s ...). See this documentation on signing commits.
• I have correctly attributed the author(s) of the code.
• I have tested the changes locally.
• I have followed the project's style guidelines.
• I have updated the documentation, if necessary.
• I have added tests, if applicable.

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Additional Notes

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