arrow

ARROW-7349: [C++] Fix the bug of parsing string hex values

std::lower_bound returns the end of the search range, when failing to find a match.

The end of the search range is one position after the last valid position. So the value in this position is undefined, and we should not reference the value here to compare it with the target value.

Closes #5993 from liyafan82/fly_1206_std and squashes the following commits:

f1e0da539 <liyafan82>  Resolve comments and add more test cases
8410712a8 <liyafan82>  Fix the bug of parsing string hex values

Authored-by: liyafan82 <fan_li_ya@foxmail.com>
Signed-off-by: Wes McKinney <wesm+git@apache.org>