Rework/redesign message replies (#9049)

Hello! This PR proposes a redesigned replying system in Zeds chat panel,
inspired by chat applications like [Slack](https://slack.com) and
[Discord](https://discord.com). Feedback and suggestions are welcome! 😄

### TODOs

- [x] Handle replies to removed messages
- [x] Add replied user's profile picture to reply indicator
- [x] Highlight the message that's been selected for replying

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### Current Status


https://github.com/zed-industries/zed/assets/146845123/4ed2c2d7-a586-48bd-973c-0d3f033e2c6b

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Release Notes:

- Redesigned message replies in the chat panel

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Co-authored-by: Thorsten Ball <mrnugget@gmail.com>