isolate consensus RPC on an optional second IPC socket

[MitkoTschimev]

Summary

Public HTTP/WS and arc-consensus share one Reth EthApi, so they share one eth_call semaphore (--rpc.max-blocking-io-requests, default 256). When client eth_call fills that queue, consensus get_signing_validator_set waits, then ETH_DEFAULT_TIMEOUT (1s) kills the CL.

--consensus-ipcpath opens a second jsonrpsee IPC on its own EthApi (16 permits) and serves eth_* plus reth_subscribePersistedBlock there. Leave it unset and consensus keeps using --ipcpath; nothing else changes.

Test plan

• arc-node-execution node --help shows --consensus-ipcpath and parsing tests pass
• Unset flag: consensus still connects to --ipcpath
• Set flag: consensus eth_call still succeeds while the public HTTP eth_call queue is saturated
• Engine API on --auth-ipc.path is unchanged

[github-actions]

Hi @MitkoTschimev,

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