arrow

ARROW-16487: [C++][Parquet] Fix parquet::Statistics::Equals() with minmax

The following cases return wrong result:

* statistics_no_minmax.Equals(statistics_no_minmax):
  This must returns true but false is returned.
* statistics_minmax.Equals(statistics_minmax):
  This must returns true but false is returned.
* statistics_minmax1.Equals(statistics_minmax2) where
  statistics_minmax1 and statistics_minmax2 have different minmax:
  This must returns false but true is returned.

Note that parquet::Statistics::Equals() was introduced by
https://github.com/apache/arrow/pull/8507 .

Closes #13087 from kou/cpp-parquet-statistics-equal

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>