Refactor ssz.go hashDefinitionVxyz

[pinebit]

🎯 Problem to be solved

To reduce code duplication and to simplify introducing new cluster definition versions, the hashing functions need to be entirely refactored using modern Golang practices.

🛠️ Proposed solution

• [ ] Check the existing code duplication among hashDefinitionVxyz() functions.
• [ ] Design and refactor a better pattern that would simplify future new fields of cluster Definition object.

🧪 Tests

The existing test coverage is already great, so rely on the existing unit tests. Also, add more in case of drastic implementation changes.

• [ ] Tested by new automated unit/integration/smoke tests