feat(next): add email, google, apple sign in

[StaberindeZA]

Because

• On the checkout page, after populating the email clicking continue should navigate the user to the FxA signin page for signin.
• On the checkout page, when clicking Google/Apple button, it should start the third party auth via FxA.
• Completion of either signin option should navigate the user back to the checkout page in a signed in state.

This pull request

• Updated Auth.js provider to support email, google and apple login
• Customers are redirected to the '/new' page on successful login, which creates a new cart with the customers uid added.
• Updates Payments Next auth config to a non-public client.

Issue that this pull request solves

Closes: #FXA-10548

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• If applicable, I have modified or added tests which pass locally.
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[xlisachan]

I was able to start the stack and sign in with Google as well as create a Mozilla account - aligned with testing signing in with Apple on stage.

r+, thanks Reino!