Tezlink/Node: mock the preapply operations RPC

Stacked on !18350 (merged).

Closes L2-90

What

Mock the preapply_operations RPC.

Why

This RPC is called from octez-client when operations are injected. We don't yet have any form of operation simulation in Tezlink so, for now, we mock this RPC.

How

We reuse the mock implementation of the simulate_operation RPC (see !18020 (merged)).

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR