Only a trial thing, not sure if I understand correctly or not but I guess only 2 entries in `bytesOfCodePointInUTF8` for the case of 6 bytes codepoint(1111110x) is enough.
Details can be found from https://en.wikipedia.org/wiki/UTF-8 in "Description" section.

Author: zhichao.li <zhichao.li@intel.com>

Closes #7582 from zhichao-li/utf8 and squashes the following commits:

8bddd01 [zhichao.li] two extra entries