Show `< 1%` when percent value evaluated is less than 1 on Stacked Progress Bar

What does this MR do?

This MR changes Stacked Progress Bar behaviour to show < 1% for when value evaluated less than 1, in order to account for values such as 0.00001 (where we don't show precision of more than 1 decimal place).

Screenshots

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [ ] Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• [ ] Conforms to the database guides

Relevant Issue

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/6028