Implemented the arrows design for threads in chat inbox. Removed the icon, and moved the unread dot logic from `chat-thread-list-item.react` to `chat-thread-list-sidebar`
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Linear Task: [[ https://linear.app/comm/issue/ENG-1779/update-design-for-threads-in-chat-inbox-on-native | ENG-1779 ]]
Depends on D5253 and D5264