[C++] String encoding detection by SIMD

[chaokunyang]

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

We've supported string ascii check using jdk8 unsafe superword in #90. But the simd string encoding check is not implemented in c++.

Describe the solution you'd like

Add simd string encoding check by SIMD by using simdutf

Additional context

https://github.com/simdjson/simdjson and it's paper https://arxiv.org/pdf/1902.08318.pdf use SIMD to speed up parsing.