[VS Code]: Use LS mapping for feature state diagnostics renderer
Problem to solve
At the moment, the VSCode repo is handling the mapping from LS values for feature state checks to user readable values. This is problematic if the diagnostics page is going to exist anywhere else.
Proposal
A previous issue has created the mapping in the LS (gitlab-org/editor-extensions/gitlab-lsp#929 (closed)). This MR utilizes the mapping from the LS directly and removes the old mapping.
There should be no functionality change here.