Persist `needs:` validation as config error

What does this MR do?

In case when needs: is missing, but when requested by service, we would not save the pipeline with config_error.

This makes it explicit that we want to persist the error as config_error failure reason.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Code review guidelines
• Style guides

Related to: https://gitlab.com/gitlab-org/gitlab-ce/issues/66983