Delete account improvements

[bryanmontz]

When a user deletes their account, we should overwrite the user's kind 0 and kind 3. Publish an empty profile that says "Account deleted" in the name fields to signal the user's intentions as much as possible, especially for relays and clients that don't support NIP-62. We should also publish an empty kind 3 after making sure that the events we want to publish get published to the user's relays.