MR Review Panel: Display full comment preview in panel
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## Proposal
Display the full comment preview instead of the text of the comment in a review
| Before | After |
| ------ | ------ |
|  |  |
### Comments from GitLab team members
From https://gitlab.com/gitlab-org/gitlab/-/issues/474794#note_2360676369
> I would really love to have a complete preview of all my pending comments in a dedicated window without having to change the page's context.
From https://gitlab.com/gitlab-org/gitlab/-/issues/474799#note_2355695909
> I was looking into the review panel in the context of viewing the unresolved comments and I am **not convinced** that the shorten entries that we use for pending reviews help when trying to get context of the threads.
### Questions
1. Are there performance considerations to this approach?
2. Are there functionality limitations like can you reference a pending comment of a review in another pending comment? If not, should the ability to "copy link" be hidden?
3. What size should the drawer be?
1. Current design is 950px but could a smaller size like 756px or 640px work?
issue