Add tooltips for the hints

[psfinaki]

Can hints themselves have tooltips? This here looks like an empty one:

It would be nice to reuse type annotation tooltips with all the good stuff like clickable references:

Looks like a function needs to be passed in
https://github.com/dotnet/roslyn/blob/315c2e149ba7889b0937d872274c33fcbfe9af5f/src/Tools/ExternalAccess/FSharp/InlineHints/FSharpInlineHint.cs

Originally posted by @kerams in #14157 (comment)

[cartermp]

I remember trying to spike on this a while back -- I don't remember exactly, but if there's some notion of a position, then you can refactor the quickinfo bits and pass that in. But I recall at the time it needing to be able to resolve a symbol in some way that the compiler service couldn't do.

[psfinaki]

@cartermp thanks for the info, this is useful.

btw @kerams by chance, is this something you would be interested in implementing? It's absolutely fine if no, just asking to avoid possible double work.

[kerams]

No, not really.