Tezlink/Node/RPC: Chain_id

What

Add support for the chain_id RPC endpoint in the Tezlink RPC directory.

Why

This MR provides access to the chain_id information through Tezlink, which is useful for clients needing to retrieve network identity via a standard RPC.

How

• Imported the chain_id RPC service from Tezos_shell_services.
• Registered the chain_id endpoint under the Tezlink RPC directory.
• New register_chain_services function to wire up the endpoint.
• New test test_tezlink_chain_id in evm_sequencer.ml to validate the endpoint.

Manually testing the MR

Run the Tezt suite and verify that test_tezlink_chain_id passes:

make octez-evm-node && dune exec etherlink/tezt/tests/main.exe -- /dal /threshold_encryption latest alpha tezlink chain_id