Notification Settings — Add Push Default On to QR-Imported Accounts

We're splitting up #11299 into two tickets, first for the initial concept of adding new accounts and, by defaulting, activating push on the inbox. This one will do the same but for accounts imported via QR codes.

Since our QR codes do not import settings, we know the user will not have set up mobile push settings, and can set them up with the preferred default of "on" for inboxes on new accounts.

AC:

• Accounts imported via QR code from desktop have "Push" enabled by default for the inbox on the account
• Tests created to ensure other import types do not enable push unless it was previously enabled, such as from K-9 to Thunderbird or from previous Thunderbird versions via file import