Explain what "coverage" and change mean for code coverage
This is an actionable insight from the [UX Department: MRs experience async critique](https://gitlab.com/gitlab-org/ux-research/-/issues/1073) research ([insight][insight]).
### What
In the merge request widget for **pipelines**, it's not clear what the word “coverage” means unless you're familiar with the concept of “code coverage”. Additionally, it's not clear what a positive/negative change in that value is comparing to.

### Why
To increase user understanding and usefulness of this information.
### How
Explain what "coverage" and change mean for code coverage
[insight]: https://dovetailapp.com/projects/14109fbc-dfdd-4204-a54e-9c80ba8b7bba/insights/eeee2096-288f-4f0f-8bf7-6893f1ceb7e7
### Proposal
* Change "coverage" to "Test Coverage"
* Add a tooltip (add to the tooltip when present for multiple coverages) with language "This change will (decrease/increase/create no change in) the overall test coverage if merged."
issue