feat: add accountNameSuggestion field to the AccountCreatedEvent

[danroc]

This PR adds an accountNameSuggestion field to the AccountCreatedEvent to allow the keyring (Snap) to make a suggestion for how the account should be named.

MetaMask is responsible for allowing the user to accept or modify the proposed name.

Examples

The Snap can call:

await this.#emitEvent(KeyringEvent.AccountCreated, {
  account,
  accountNameSuggestion: "My Account",
});

[danroc]

Converting to draft to explore the idea of including the account name suggestion in the Snap's manifest.