[NT-552] Fix selecting card regression

[ifbarrera]

📲 What

Fixes a regression introduced in #944 whereby if you added a new card, then selected a different card, you couldn't re-select the newly added card.

🛠 How

Refactors the approach for adding a new card slightly. We brought back the scan, and fed the result (allCards) to the self.updateSelectedCreditCard signal. Also adds a test to cover this case.

👀 See

Trello, screenshots, external resources?

Before 🐛	After 🦋

♿️ Accessibility

N/A

🏎 Performance

N/A

✅ Acceptance criteria

• On the pledge screen, add a new card. You should see the new card selected. Then, select a different card from the list. Then, re-select the newly added card. The card should select properly.

[justinswart]

Great, "checks out!"