[clang] [clang] Cover CWG issues about `export template` (PR #94876)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

The goal of the status page is to convey implementation status to our users, and so from that perspective I think N/A provides the least information to users because it basically says "this entry doesn't apply to us". So in these kinds of cases, `sup` conveys more information because the DRs would apply to us, except another DR superseded the need for making the changes.

In terms of the color used, we want green to mean "we're behaving in a conforming way" so users can tell at a glance where the edge cases are. This case is a bit weird because "conform" means we *don't* implement something rather than we *do* implement it, but I still think green is appropriate because we're following the standard. It might be fine to give a different color to superseded, but I would guess we'd want that to be a lighter form version of whatever the superseding issue is colored. e.g., given that conforming = green and non-conforming = red, if we have a superseded issue we conform to, it would be light green, and if we didn't conform it would be pink. WDYT?

https://github.com/llvm/llvm-project/pull/94876