introduce `stringForReactionList` in reaction-utils. This is a refactor where D5813 and D5814 were using the same logic in `web` and `native`, so we should put that logic into a helper function in `lib`. We then can call the function from `web` and `native` and get the same results
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Depends on D5812
Linear Task: [[ https://linear.app/comm/issue/ENG-2247/fetching-message-likes | ENG-2247 ]]