Adjusting display of CompletionItem

[ksss]

There are two problems with the current completion function.

• If I want to complete a method such as default_value, def part will be completed.
• Type parameters are also being completed.

before-10.mov

So, the following fixes have been made.

• Remove the def part from the completion target.
• Remove type parameters from the completion target as well. Instead, put type parameters in detail.

This solves the problem, but the downside is that the type parameter that used to show up in all completion lists is now only the one you have selected.

after-10.mov

[soutaro]

Looks great! Thank you for sending the patch!

(I was thinking of using filterText attribute in fact, but deleting def and the types would look better.)