chore(PSDK-640): add networkId to WalletData

[0xRAG]

What changed? Why?

It should be clear which saved wallets belong to which networks when you save_seed / export_data for a given wallet.

How i tested

After running:

const wallet = await Wallet.create({
  networkId: Coinbase.networks.BaseSepolia,
});

wallet.saveSeed("/Users/ryan/code/public/seeds/wallet_seed.json");

wallet_seed.json looks like:

{
  "f737686d-c78f-4b89-9bf4-7b57559425b8": {
    "seed": "8a5xxx",
    "encrypted": false,
    "authTag": "",
    "iv": "",
    "networkId": "base-sepolia"
  }
}

And the result of wallet.export():

{
  walletId: 'f737686d-c78f-4b89-9bf4-7b57559425b8',
  seed: '8a5xxx',
  networkId: 'base-sepolia'
}

Qualified Impact

The network id should always be present, and if it is not, it will simply not be included in the WalletData

[cb-heimdall]

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