feat: log editor language ID

Currently the Code Suggestions backend looks at the file extension to determine what language the code might be. If the user overrides the language setting in the client, the backend should know about it. This commit only logs the editor_lang in the Prometheus language counters so we can see how often the guessed language matches the editor's language.

This requires an update to the client: gitlab-org/gitlab-vscode-extension!1004 (merged)