fix(bg/storage): store user provided wallet URL as well

[sidvishnoi]

Context

Useful with #1029
Some wallet URLs have redirects, and the resulting resourceServer could be something that corresponds to a different wallet as well.

With this info stored, we can:

• help distinguish those redirect wallets (MMAON, ilp.dev) from their managing wallets
• display the wallet address that user entered in UI - like UI showing ilp.dev instead of ilp.interledger.cards address (not done yet)

Changes proposed in this pull request

• Store walletAddressUrl as walletAddress.url in extension storage.
  • The url property isn't part of standard WalletAddress response, so it's safe to add to storage within this object.
  • The field is marked optional as it doesn't exist on already connected wallets.

---

Example: User input $ilp.interledger-test.dev/sid at connectWallet gets stored like this:

[github-actions]

Extension builds preview

Name	Link
Latest commit	6807719
Latest job logs	Run #14732184460
	Download
	Download