[ES|QL] Provide hover information

[dej611]

Describe the feature:

This feature could be really useful to help users debug their own query via metadata overview. To make a comparison with Lens formula UX, in there hover works only for functions:

I think in ES|QL this can be way more powerful, here some ideas I've already attempted as PoC:

• provide policy metadata information on hover (i.e. which is the target index, what fields will be imported from there, etc...) ✨

• provide a table preview at a specific point in the query ✨

• more..?

[elasticmachine]

Pinging @elastic/kibana-visualizations (Team:Visualizations)

[elasticmachine]

Pinging @elastic/kibana-esql (Team:ESQL)