[MAINTAIN] Investigate circular and isloated dependencies in MAVA Redesign

[AsadJeewa]

Please describe what needs to be maintained

The Guardrails PR https://github.com/instadeepai/Mava/pull/596 highlighted some non-breaking issues that we should revisit.

• Step and EpochUpdate are both dependent on each other
• ParallelSequqnceAdder, ExtraLogProbSpec and ExecutorInit are isolated

Describe the outcome you'd like

All isolated nodes should be pruned (such as ExecutorInit) or explained by inheritance (ParallelSequqnceAdder) or Optionality (ExecutorInit)

How do we know when maintenance is complete?

Checklist:

• [ ] Refactor PR merged into dev with MAPPO system still running as before