[Java][vertx] Use typeMapping instead of postProcessParameter

[wing328]

• Use typeMapping instead of postProcessParameter to map UUID, Date, DateTime into String

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cc @bbdouglas (2017/07) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09) @jeff9finger (2018/01) @karismann (2019/03) @Zomzog (2019/04) @lwlee2608 (2019/10) @bkabrda (2020/01)

[slinkydeveloper]

I see, makes sense to me. Thank you!