feat(next): add auth statsd and error page

[StaberindeZA]

Because

• In an attempt to have statsd for all 3rd party dependencies, add statsd recording to Auth.js actions and events.
• On auth error, users are navigated to Auth.js default error page

This pull request

• Add statsd counters signin, signout, prompt_none_fail and error
• Add custom Auth.js error page

Issue that this pull request solves

Closes: #FXA-11670 #FXA-11754

Checklist

Put an x in the boxes that apply

• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).

Screenshots (Optional)

To get to this Error Page follow these steps

1. Navigate to Checkout, enter email and hit "Sign in"
2. When on the FxA page, copy the URL
3. Complete the FxA Sign In, and navigate back to Checkout successfully
4. Open the copied URL into a new tab. This should load the FxA sign in page. Complete Sign In again
5. The new error page should be shown

[xlisachan]

## Group level comment
[empty newline]
string-1 = Foo
# Individual comment
string-2 = Bar

Sauce: #18932 (comment)