DAC: `RPC_server` code organization reflects code versioning

Context

Part of #5437 (closed), follows !8762 (merged).

This MR organizes code inside RPC_server into V0, V1 and Shared_by_V0_and_V1. As requested by the reviewers we additionally move all the handlers to RPC_handlers. The same module organisation is used inside RPC_handlers, as it is used inside RPC_server.

This is important since now we are going to work on releasing V1 iteretively. This explicitness will prevent us from having undesired effects, by accidentally modifying a shared handler.

Additionally, as you can see at the Rpc_server.start, we explicitly register dynamic_rpc_dir for both V0 or V1 modules separately. This proves to be handy in the follow up (!8841 (merged))

See !8841 (merged) for the follow-up: It introduces allow-v1 feature flag.

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