Update testing scripts

[Keyrxng]

Requires #274

The linked PR introduces support for stacked permits and extends multi-network capabilities.

Proposed changes for streamlined testing:

• Setup two Anvil instances:

  • One targeting Gnosis (current setup).
  • Another targeting Ethereum.

• Configuration requirements:

  • The new instance should operate on port 8546 with networkId 31338.

• Funding script updates:

  • Update the funding script to reflect the "whale" address as the updated "WXDAI" token holder for this network.
  • Set distinct approvals and balances compared to the first instance for clarity.

• Script adjustments:

  • Eliminate process.env usage and hardcode necessary values to enhance clarity and prevent operational errors during script execution.

• Permit generation:

  • Generate two permits from the original instance and one from the new instance, to avoid breaking old tests.

• Additional testing scripts:

  • Introduce test:anvil-eth and test:fund-eth scripts, to be utilized only when testing this feature.

• RPC Handler Update:

  • Implement a NODE_ENV check in use-rpc-handler to ensure compatibility:

    return new ethers.providers.JsonRpcProvider(
      networkId === 31337 ? "http://localhost:8545" : "http://localhost:8546", networkId
    );

    This ensures the correct provider is returned since 31338 is not a supported network in the rpcHandler package

time: 2 hours