[action][app_store_build_number] Added the missing unit tests

[crazymanish]

Checklist

• I've run bundle exec rspec from the root directory to see all new and existing tests pass
• I've followed the fastlane code style and run bundle exec rubocop -a to ensure the code style is valid
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.

Motivation and Context

• Notice that app_store_build_number unit tests are missing for the important functionality.
  (There are still a couple of cases that needs to cover in unit tests, I will open new PR on top of this....this PR is already big more than 200lines)

In this PR

• Added unit tests to get the live-version build number
• Added unit tests to get the testflight build number

Testing Steps

• Checkout this PR and
• Run bundle exec rspec fastlane/spec/actions_specs/app_store_build_number_spec.rb

Screenshot

[joshdholtz]

I looovvvveee this missing unit test PRs ❤️ Thank you thank you!

[fastlane-bot]

Hey @crazymanish 👋

Thank you for your contribution to fastlane and congrats on getting this pull request merged 🎉
The code change now lives in the master branch, however it wasn't released to RubyGems yet.
We usually ship about once a week, and your PR will be included in the next one.

Please let us know if this change requires an immediate release by adding a comment here 👍
We'll notify you once we shipped a new release with your changes 🚀

[fastlane-bot]

Congratulations! 🎉 This was released as part of fastlane 2.185.0 🚀