Cleanup specs

What does this MR do and why?

Spin off work from Support multiple devfile binaries on "Ruby" pla... (!74 - merged) , particularly this comment: !74 (comment 2431610617)+

This MR cleans up the specs to align with rspec best practices and overall DRY principles.

• It uses parametized specs to run common specs across all devfile versions
• It uses shared examples to run invalid devfile specs
• We duplicated the get_ingress spec in the invalid examples, so I removed that duplication
• some of the lets are not ever reinitialized, so I just made the constants instead of using let_it_be would need to include the whole test_prof gem, not worth it IMO but I don't mind.

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