feat(rpc): support new x402 updates and Arc Testnet faucet drips

[johnpmitsch]

Summary

• Add arc-testnet payment-network and USDC resolution.
• Accept Arc transaction-hash drips and Circle transfer-ID drips.
• Render the settlement identifier and update CLI guidance.
• Use released quicknode-sdk 0.8.2.

Test plan

• cargo check
• cargo test
• cargo clippy --all-targets -- -D warnings
• cargo fmt --check
• cargo build --release