"Copy value" on strings with size larger than 64 should copy the entire string regardless of the maxStringLen setting

vscode 1.30.1
go ext 0.8.0
dlv 1.0.0

It's fine to show "...+27 more" when it doesn't fit. But it's totally unexpected copy this as a part of the string.

I see Issue #868 tells the same and it's closed. So I guess it's a little bit different issue.
