[Long term] Replace popover/tooltip positioning logic with new CSS anchor positioning

[cee-chen]

⚠️ The new CSS anchor positioning spec is not yet implemented by all browsers and its API is not yet stable. This functionality is not ready to use within the next ~year or so, but we should keep an eye on its progress and be ready to replace our popover and tooltip components with it once it's ready to use.

A helpful preview of its functionality in Chrome, well worth checking out: https://developer.chrome.com/blog/tether-elements-to-each-other-with-css-anchor-positioning/

Feature status:

• https://caniuse.com/css-anchor-positioning
• https://www.w3.org/TR/css-anchor-position-1/
• https://chromestatus.com/feature/5124922471874560

[JasonStoltz]

We prioritized this as low for now, since adoption is not quite there. We haven't assigned this a size yet, as we don't know what the effort will be. We'd like to revisit this in the future when the spec is more established.

[github-actions[bot]]

👋 Hi there - this issue hasn't had any activity in 6 months. If the EUI team has not explicitly expressed that this is something on our roadmap, it's unlikely that we'll pick this issue up. We would sincerely appreciate a PR/community contribution if this is something that matters to you! If not, and there is no further activity on this issue for another 6 months (i.e. it's stale for over a year), the issue will be auto-closed.