[Empty state section] Improve spacings

[jeremie-lucca]

Spacing between description and free content (emptyState-actions) is handled by <p> default spacing, which cannot be edited as part of our component and can lead to extra spacing on component's bottom when free content is not provided. A better approach would be to remove this spacing, add it on emptyState-actions, and remove emptyState-actions from DOM when free content is not provided.