chore: add gitlab version and client type to metrics

What does this merge request do and why?

This MR adds gitlab_version and client_type to prometheus metrics as labels.

Part of #1571 (closed)

How to set up and validate locally

1. Run a workflow
2. Go to prometheus metrics server
3. You should see metrics having label with gitlab_version
4. You should see metrics having client_type = "unknown" until gitlab-org/editor-extensions/gitlab-lsp!2218 (merged) is released.

Merge request checklist

• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.
• If this change requires executor implementation: verified that issues/MRs exist for both Go executor and Node executor or confirmed that changes are backward-compatible and don't break existing executor functionality.