fix(Auth): Add correct validation for initial state when executing confirm sign in

[harsh62]

#2586

There are 2 changes being made:

• Introduce sending of the confirmSignIn event outside of the state machine listener.
• When in waitingForAnswer state, validate and return the nextStep based on the result

Description of changes:

Check points: (check or cross out if not relevant)

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• All integration tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[atierian]

Do you think a labeled statement (maybe StateSequenceLoop) could help here to clearly see the loop's control flow points?