[VS Code]: Add GitLab instance version to the diagnostics

Problem

When the user copy-pastes their diagnostics to a Zendesk/GitLab issue, we want to known their GitLab instance version

Solution

We introduced version diagnostics provider in [VS Code]: Version Diagnostics Section + Diagno... (#1761 - closed), this issue should add the last line: GitLab instance version

This version will change every time we change the active account (so the version provider must listen on account changes).