Tezlink : Add dummy simulate operation service to Tezlink

What

Inspiration from @rafoo_ commit Stub implementation of the simulate_operation RPC added to the Tezlink block services.

Why

This is a preliminary step toward full support for simulate_operation, allowing dependent tooling to begin integrating with the endpoint. It unblocks demo relying on its availability while clearly marking it as a temporary solution.

How

• Imported the simulate_operation RPC from the protocol plugin.
• Registered it in tezos_services.ml with a stub implementation returning the original operation protocol data and mock receipts.
• Added Mock.dummy_receipts to simulate a typical transaction result structure.
• Included a TODO referencing the upstream issue for full implementation: #7965

Manually testing the MR