Improve metrics details UI when no data available

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/138934



Merged-by: Phil Hughes <me@iamphill.com>
Approved-by: Minahil Nichols <minahilnichols@gitlab.com>
Approved-by: Phil Hughes <me@iamphill.com>
Reviewed-by: Daniele Rossetti <drossetti@gitlab.com>
Co-authored-by: Daniele Rossetti <drossetti@gitlab.com>