Additional tests for ios_get_app_version

[iangmaia]

What does it do?

This PR improves the existing method Ios::VersionHelper::read_from_config_file(), making it more reliable and robust by using the gem xcodeproj, as well as adding better error handling. Some additional tests cases were also implemented.

This need came up as I was testing the code and noticed that possible format variations for the .xcconfig file were not being treated properly and there was no error handling.

Related PRs

• Note: this PR was originally created in a separate fork. See original review and discussions: Additional tests for ios_get_app_version iangmaia/release-toolkit#1
• This PR builds on top of #445

Checklist before requesting a review

• Run bundle exec rubocop to test for code style violations and recommendations
• Add Unit Tests (aka specs/*_spec.rb) if applicable
• Run bundle exec rspec to run the whole test suite and ensure all your tests pass
• Make sure you added an entry in the CHANGELOG.md file to describe your changes under the approprioate existing ### subsection of the existing ## Trunk section.

[AliSoftware]

Already reviewed as part of iangmaia#1

Please add a CHANGELOG entry (under the Internal Changes section) first though

[iangmaia]

Already reviewed as part of iangmaia#1

Please add a CHANGELOG entry (under the Internal Changes section) first though

Done.