Drop use of "legacy" in favor of "unsupported" and use new info framework instead of warnings

[Mgrmjp]

Why are newer version legacy.

Confusing. 😱

[pirog]

We are just using https://endoflife.date/mariadb to determine supported/unsupported. I think the confusion is probably from the word "legacy" which made more sense five years ago when it was more or less a proxy for unsupported.

I think we should probably just change the word "legacy" to "unsupported" and link to https://endoflife.date when relevant. I'm going to move this issue into core because improvements should likely happen there.

Feel free to spin up another issue here, or submit a PR, to update the docs with new the new language and a link to https://endoflife.date/mariadb

[pirog]

This would probably be a good place to scope creep and introduce api4 service routing since that will also be version dependent and is related.