The hover interaction should show short form docs

[rockstar]

Right now, the hover information shows type information. In many cases, this type information is hyper-technical, and not so helpful. The best solution for hover information is probably the docs, and specifically the short-form docs.

DOD:

• textDocument/hover provides short form docs on functions.

Stretch:

• Providing a link to the long form docs is a great idea, but some clients may have problems rendering hyperlinks. Check that before adding more text than necessary.

[Marwes]

The PackageExports that is embedded in the flux crate now contains the comments for each export which should be usable to display the docs https://github.com/influxdata/flux/pull/4774