Improve perceived performance of comment loading experience
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## Problem
- MRs with tons of comments and activity take a long time to load and are overwhelming to read
## Potential solutions
- [Expand middle of activity feed when it reaches a threshold](https://gitlab.com/gitlab-org/gitlab/-/issues/356785#note_2559730631)
- [Pagination](https://gitlab.com/gitlab-org/gitlab/-/issues/356785#note_2559761868)
- [Collapse similar activity](https://gitlab.com/gitlab-org/gitlab/-/issues/356785#note_2561473251)
- [Add activity type filter](https://gitlab.com/gitlab-org/gitlab/-/issues/356785#note_2561479547)
- [De-select less important activity items](https://gitlab.com/gitlab-org/gitlab/-/issues/356785#note_2562115913)
- [Separating comments from activity log](https://gitlab.com/gitlab-org/gitlab/-/issues/356785#note_2578796549)
issue