Rpc process: introduce dummy monitor daemon

This MR aims to introduce a monitoring daemon into the rpc_process. This will be useful in !9490 (merged), to monitor the new blocks received by the node to trigger the synchronisation of the rpc_process.

Here, the monitoring daemon is a dummy one as it does nothing. It just emit an event. The Store.sync will be plugged in !9490 (merged).

This MR is on top of !11309 (merged) and !11310 (merged)

Manually testing the MR

Green CI and notice the expected info events when the rpc process will receive new heads

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