Add a linter to make sure deprecated flag is also applied to children

[saschanaz]

See https://github.com/mdn/browser-compat-data/pull/7311/files#r522266719

[queengooborg]

+1 for this. Should we also extend this to experimental?

[saschanaz]

Good idea! I'll do that as a followup, as the current PR already modifies multiple files and I see some issues there.

[queengooborg]

I was going through the list of PRs, and I noticed that you have a linter written for preventing both experimental and deprecated together (#6813). I'm thinking that it would make sense to combine all three linter functions (deprecated consistency, experimental consistency, and no deprecated and experimental together) into a single test-status.js file? (Future plan still, but it'll certainly help reduce the amount of repeated code we have.)

[saschanaz]

Yay good idea, just renamed both to test-status.js. I can rebase them once either one is merged.

[caugner]

Fixed via #24810.