Unconditional Gateway Deployment and Refinements

[karlem]

Description:
Enhance the gateway deployment process to allow unconditional deployment, even in unanchored mode. Refactor related methods for clarity and enforce restrictions on operations requiring a parent subnet.

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Tasks:

1. Unconditional Deployment

   • Add a constructor parameter (e.g., isAnchored) to define if the gateway is running anchored or unanchored.
   • Update gateway initialization to handle unanchored mode appropriately.

2. Refactor Pathways for Root Gateways

   • Extend is_root logic to also cover unanchored mode (e.g., subnet_id == null).
   • Introduce a helper method (isUnanchoredOrRoot()) to centralize this logic.

3. Rename gateway.enabled()

   • Rename gateway.enabled() to gateway.isAnchored() for improved clarity.
   • Update all references and document the change.

4. Restrict Parent-Dependent Methods

   • Prohibit operations requiring a parent (e.g., sending bottom-up messages) for unanchored or root gateways.
   • Add validation logic in relevant methods with clear revert messages.

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Goal:
Allow flexible deployment of gateways while maintaining clear semantics and safeguarding operations that rely on anchored state.

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Additional Notes:
Please ensure tests are updated or added for the new constructor behavior, pathway logic, and restricted methods.