Split green_screen

BUR #33477 has been rejected.

deprecate green_screen

green_screen tag is currently used for both templates (e.g. post #7188284, post #7259999, post #4535991) and chroma keys as objects (e.g. post #7998468, post #6878502, post #3308542), and they arguably don't belong on the same tag.

So, my proposal for successor tag names is:

• chroma_key_(template) - for templates, with possible implication of the template tag. This includes both plain green/blue backgrounds and images with plain green/blue parts, like post #3579137.
• chroma_key_(object) - for chroma keys as objects, self-explanatory.

The chroma_key name is chosen because chroma key backgrounds aren't always green. In this case, green_screen_* tags should be aliases of their respective chroma_key_* tags.

I don't like the lack of an alias; green screen is infinitely more searchable to me as someone without knowledge of what chroma keys are (more specifically, I didn't know what they were called, but called them "green screens" regardless of if they were meme templates or physical green screens). No opinion on if they actually should be independently tagged concepts but not a fan of not aliasing green screen at all and opting for a flat deprecation.

This bulk update request is pending automatic rejection in 5 days.

This bulk update request has been rejected because it was not approved within 45 days.

The bulk update request #33477 (forum #318238) has been rejected by @DanbooruBot.