right now we use fastjson2 (in Collector, Source, etc), but as there be an
embedded jackson provided in flink, we doubt if it be worthy to migrate to
using it instead.
we take care of performance very much so if there be some performance
benchmark please let us know...
Also I'm kind of confused, so if the flink jackson have better
performance, please give a link of how we shall use it now... passing
JsonNode seems to be 'old style' by FLINK-32610
<https://issues.apache.org/jira/browse/FLINK-32610>, but I didn't find a
new usage guide...
