[KED-1647] Refactor random data generator, and add layers

[richardwestenra]

Description

1. I realised some ways that the random data generator creates nodes/edges could be improved and simplified.
2. I needed to add layers to the random data generator

Development notes

The random data generator now assigns layers in a way that make the ranks towards the top have more nodes than the ones at the bottom, which is more in line with how charts should behave in reality.

I've also randomly assigned the number of ranks per layer, so that they will grow and shrink each time.

Checklist

• Read the contributing guidelines
• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added new entries to the RELEASE.md file
• Added tests to cover my changes

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