Add color to the badges in the MR homepage
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## Proposal
Use color on the badges to help differentiation of the different merge requests.
| Badge | Assignee/author actions | Reviewer actions |
| ------ | ------ | ------ |
| neutral-muted (gray) | `Waiting for approval`, `# approval required` | `# approval required`, `You requested changes`, `You commented`, `Approved` |
| warning (yellow) | `Draft`, `Reviewers needed` | `Requested` |
| info (blue) | `Reviewer commented` | `Review started` |
| error (red) | `Changes requested` | |
| success (green) | `Ready to merge` | |
## Background
We have already started introducing the `success` (green) badges when merge checks have passed in https://gitlab.com/gitlab-org/gitlab/-/merge_requests/183524
Feedback received that this would be useful
1. https://gitlab.com/gitlab-org/gitlab/-/issues/512314#note_2296778901
2. https://gitlab.com/gitlab-org/gitlab/-/issues/512314#note_2298862467
3. https://gitlab.com/gitlab-org/gitlab/-/issues/457731#note_2428524566
4. [3400#color-action-status-help-identify-what-needs-your-attention](https://gitlab.com/gitlab-org/ux-research/-/issues/3400#color-action-status-help-identify-what-needs-your-attention)
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