Fix hover

[michaelmesser]

Hover sometimes doesn't return the correct value.

f : Bool -> Bool
f = \case
    True => False
    False => True
          *  ^

If a save, then hover over ^ I get Prelude.True : Bool. However, if I hover over * then hover over ^, I get Test.case block in f : Bool -> Bool. Is this caused by overlapping ranges being added to the cache?

Also, for a better user experience hover should return a range.

I tried to fix this at one point but ran into idris-lang/Idris2#1506 and idris-lang/Idris2#1543

Additionally hover should show documentation. There also is probably a better way to handle hiding/showing implicit arguments.

[ianmelendez95]

If anyone else is having an issue with this, I've found a quick way to 'reset' is to just edit the line (I add a space and remove it), save the file again, and then move up and down to get it to reload the arguments.