perf: x/genutil/types: AppGenesisFromFile and AppGenesisFromReader are unnecessarily inefficient by fully slurping the io.Reader to RAM then invoking json.Unmarshal then attempting on error to invoke cometbft/cmtjson.Unmarshal

perf: x/genutil/types: AppGenesisFromFile and AppGenesisFromReader are unnecessarily inefficient by fully slurping the io.Reader to RAM then invoking json.Unmarshal then attempting on error to invoke cometbft/cmtjson.Unmarshal #2727