Allow collapsing comments in the pending state code review
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## Why are we doing this work
Allow viewing the code without pending comments.
When reviewing a merge request, I am leaving comments that are not yet published (show as comments in pending state). I would like to be able to collapse/expand these comments to allow me to view the code without distracting pending comments before submitting the review.
{width="691" height="196"}
## Relevant links
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- [Design Issue](https://gitlab.com/gitlab-org/gitlab/-/issues/<id>)
- [Design 1](https://gitlab.com/gitlab-org/gitlab/-/issues/<id>/designs/<image>.png)
- [Design 2](https://gitlab.com/gitlab-org/gitlab/-/issues/<id>/designs/<image>.png)
- [Similar implementation](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/<id>)-->
## Non-functional requirements
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- [ ] Documentation:
- [ ] Feature flag:
- [ ] Performance:
- [ ] Testing:
## Implementation plan
The exact implementation detail TBA.
I proposed adding a collapse button as per the image below.
<details>
<summary>images</summary>


{width="697" height="208"}
</details>
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## Verification steps
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issue