cli: Relax graph path requirements

We want to be able to run rpc and grpc instances independently from one another. Currently, the cli imposes the use of the graph path for both services. Which makes the deployment in that setup complex (with configuration duplication).

As far as I understood it, the current implementation only requires the grpc to have access to the graph files. It'd be neat we relax the cli's constraint if it's possible.

A proposal mr has been opened to solve this.

[1] !662 (merged)