Add setNewArch command unit tests - #2747

Summary

• Add unit tests for setNewArch Android gradle.properties updates when newArchEnabled exists or is missing.
• Add unit tests for iOS Podfile New Architecture enable/disable paths and user cancellation.
• Fix the InternalErrorCode typo from FaiedToSetNewArch to FailedToSetNewArch.

Test Plan

• npx gulp format
• npx tsc --noEmit
• npx mocha --ui tdd test\extension\commands\setNewArch.test.js
• npm test

Closes #2731