peadm::convert & peadm::upgrade: move steps to own datatypes

[bastelfreak]

This makes the whole plan more readable because we don't need multiple lines in the plan.

Summary

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Additional Context

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Related Issues (if any)

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Checklist

• [ ] 🟢 Spec tests.
• [ ] 🟢 Acceptance tests.

Changes include test coverage?

• [ ] Yes
• [ ] Not needed

Have you updated the documentation?

• [ ] Yes, I've updated the appropriate docs
• [ ] Not needed