Context

This patch make the rpc process respond to /config without forwarding to the node.

Manually testing the MR

run

TEZOS_LOG="rpc-process->debug" ./octez-node run --rpc-addr 127.0.0.1:8732

then call

./octez-client rpc get /config

and ensure none of the following print appears

Jul 05 11:38:14.264: forwarding to the node : /config

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).
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