Enable ethereum rpc endpoints for farmerless dev node

[jfrank-summit]

Summary

Adds Ethereum JSON-RPC support to EVM domain nodes built via domain-test-service, enabling the farmerless dev node to expose both Substrate and Ethereum RPC endpoints when running with --domain.

Motivation

The farmerless dev node successfully starts an EVM domain when using the --domain flag, but it only exposed Substrate RPC endpoints. Ethereum-specific endpoints (eth_call, eth_sendTransaction, eth_chainId, etc.) were missing because the domain node was built with DefaultProvider instead of EthProvider.

This prevented developers from testing Ethereum-compatible dApps and smart contracts against the dev node.

Implementation Details

Changes

1. Made DomainNode::build generic over Provider (private internal function)

   • Added type parameter with appropriate trait bounds
   • Allows passing either DefaultProvider or EthProvider

2. EVM domains now use EthProvider

   • build_evm_node() and build_evm_node_with() create an EthProvider
   • Configures Frontier (Ethereum compatibility layer) with sensible defaults
   • Enables dev signer for easy transaction testing

Configuration Values

The EthConfiguration uses CLI defaults from domain-eth-service, with one intentional change:

• enable_dev_signer: true — Exposes pre-funded dev accounts via eth_accounts RPC

Dependencies

Added to domain-test-service:

• domain-eth-service — Core dependency providing EthProvider
• domain-block-preprocessor — Required for Provider trait bounds
• sc-transaction-pool — Required for Provider trait bounds

All dependencies already exist in the workspace.

Testing

# Start farmerless dev node with EVM domain
cargo run -p subspace-farmerless-dev-node -- --domain --domain-rpc-port 9945

# Test Ethereum RPC (new functionality)
curl -X POST http://127.0.0.1:9945 \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_chainId","params":[],"id":1}'

# Should return chain ID instead of "method not found"

Code contributor checklist:

• I have read, understood and followed contributing guide

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