parent tests

[kim-tsao]

What does this PR do?:

Extend the API tests to include coverage for testing parent overrides, new utils to support the overrides, and other refactoring changes

Which issue(s) this PR fixes:

#510

PR acceptance criteria:

Testing and documentation do not need to be complete in order for this PR to be approved. We just need to ensure tracking issues are opened.

• Open new test/doc issues under the devfile/api repo
• Check each criteria if:
• There is a separate tracking issue. Add the issue link under the criteria
  or
• test/doc updates are made as part of this PR
• If unchecked, explain why it's not needed

• [ X] Unit/Functional tests

• QE Integration test
  These are unit tests only

• Documentation
  No changes needed for docs

• Client Impact
  No

How to test changes / Special notes to the reviewer:

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: kim-tsao, maysunfaisal

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• OWNERS

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