[uiSettings] allow to enhance categories / add category related fields

[pgayvallet]

Currently, there is no real representation or model of a setting's category, as the category list is only inferred from the category field on the registered settings, which is just a label.

This introduces a lot of limitations, as we can't enhance the categories or section in any way.

In example, in #17298, we would need to add a description associated with the category, and we were blocked by that.

We should revisit the way category are defined and represented. We may want to add a new API to allow registering categories for the uiSettings service.

Also need to see how to support BWC with categories that would only be represented by the category field of the settings.

And also, to adapt the advancedSettings usages of the categories.

[elasticmachine]

Pinging @elastic/kibana-core (Team:Core)

[TinaHeiligers]

There hasn't been any movement or new comments made to this issue in > 1 year. As such, this issue is being closed as stale.
Feel free to reopen if needed.