fix(migrate-template-gen): return early if output is not Fn:GetAtt or…

[abhi7cr]

Description of changes

• Exit early in the output resolver if the template ouput is not of type Ref or Fn::GetAtt. Currently, the resources that are moved over only depend on outputs with these types. So its safe to return early. We can add additional cases if we discover its required during migration
• At the final step of revert command, delete the current amplify folder (Gen2) and move the backup Gen1 folder (.amplify/migration/amplify) to amplify

Issue #, if available

Description of how you validated changes

ran execute and revert command locally, unit tests.

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)
• New AWS SDK calls or CloudFormation actions have been added to relevant test and service IAM policies
• Pull request labels are added

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Approved from integration tests github account by mistake