This reads cleaner, and lets us directly access the SIWEResult from the error-handling code (needed in a later diff).

Note that this changes the error handling slightly. Whereas previously, onFailure would only get triggered if the SIWE call to the keyserver rejected, now it can get rejected if any of the earlier calls reject:

1. await logInExtraInfo
2. await getInitialNotificationsEncryptedMessage

I think it's probably a good thing to show the user an error in these cases.

Depends on D10412

I tested this diff stack as follows:

1. Delete test ETH account 1. Attempt to do main SIWE login with ETH account 1. Confirm it redirects to registration flow. Complete registration flow and confirm account successfully created
2. Same as above, but go back after reaching the avatar screen, and then forward to see the Ethereum screen. Choose the option to use the already connected ETH account, then complete registration flow and confirm account successfully created
3. Same as above, except in the Ethereum screen, choose the option to "skip" the Ethereum login. Confirm password account is successfully created
4. Same as above, except in the Ethereum screen, select another Ethereum wallet that already has a Comm account. Confirm that we hit ExistingEthereumAccount, and that we're able to login directly with the existing account
5. Same as above, except in the Ethereum screen, select another Ethereum wallet that doesn't already have a Comm account. Confirm that the account is successfully created using the second Ethereum wallet and not the first
6. Same as above, except in the Ethereum screen, go through the auth flow again for the exact same wallet. Confirm that the account is successfully created

Note that I needed to apply this patch to work around ENG-6097.