introduced `reactions` to chat item height measurer. This is necessary to because in `native/chat/message-list-container` we measure the messages first and then pass the message list data with heights down to `MessageList` which will eventually then be used by `InlineSidebar`
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Depends on D5812
Linear Task: [[ https://linear.app/comm/issue/ENG-2408/handle-message-reactions-on-native-ui | ENG-2408 ]]