Use Network ID to determine the correct faucet to use

[mvadari]

Code reference: https://github.com/XRPLF/xrpl.js/blob/main/packages/xrpl/src/Wallet/fundWallet.ts

Currently, the faucet generation code guesses the correct faucet to use based on substrings in the URL. This isn't a very robust system. It would be better (and more robust) to use the Network ID.