feat(): route entire slice subnet via hub for spoke-to-spoke (#304)

[Shreesha001]

Description

Enables spoke-to-spoke traffic in HubAndSpoke topology on the controller side:

• Marks each spoke's gateway with RouteEntireSliceSubnet=true so the spoke sends the whole slice to the hub, which relays it to other spokes.
• Keeps the flag correct on topology changes: sets it on spokes, clears it on hubs (a hub must never route the whole slice).
• Adds gateway connection-status fields to the WorkerSliceGateway CRD (for #471).
• Adds an end-to-end test proving HubAndSpoke builds a partial mesh (no spoke-to-spoke gateway).

Fixes #304

How Has This Been Tested?

• HubAndSpoke creates 4 gateways: hub=Server, spoke=Client with the flag; no spoke-to-spoke gateway.
• Switching FullMesh <-> HubAndSpoke and changing the hub keeps the flag correct (no stale flags).
• Adding/removing a spoke works.
• Same result with Wireguard.
• FullMesh slices are unchanged.
• Real cluster: spoke-to-spoke iperf ~4.4 Mbit/s; gateway failover recovers.
• go build clean; unit tests pass.

Checklist:

• The title states what changed and the related issue number.
• I have performed a self-review of my own code.
• I have commented my code in hard-to-understand areas.
• I have added the required unit test cases.

Does this PR introduce a breaking change for other components like worker-operator?

No. The new fields are additive. The feature works when paired with worker-operator #496 and #495.