Migrate nlohmann json to tencent rapidjson

[testillano]

Is your feature request related to a problem? Please describe.

It is not strictly a problem use nlohmann json library, as its performance is very good.
But in general, rapidjson is faster and more efficient, so, we should try to give a chance for this migration.
Check benchmarking tests here: https://github.com/miloyip/nativejson-benchmark

[testillano]

Consider also to implement an LRU cache when building rapidjson::Pointer objects.
You could use this one, which works right: https://github.com/lamerman/cpp-lru-cache/blob/master/include/lrucache.hpp