[Initiative] Add support for single-sourced license level information

### Summary

https://www.elastic.co/subscriptions is the source of truth for feature licensing information. We do not list specific licensing information in the docs as it inevitably changes over time.

In V3, we should explore the ability to single-source feature licensing information. For example, if we had a single yaml or json file that the product team could add licensing information to, we could potentially show specific license levels in the docs. IMO, this would be a better user experience than forcing folks to go to a different page to determine if the feature they want to use is supported by their current subscription.

Alternatively, from a Slack convo:

> It makes sense to not scatter subscriptions all over the docs. I just had a hard time figuring out which one was related to this feature. Maybe all features in the subscriptions page should have anchors that doc pages can link to directly