[SPARK-8309] [CORE] Support for more than 12M items in OpenHashMap

The problem occurs because the position mask `0xEFFFFFF` is incorrect. It has zero 25th bit, so when capacity grows beyond 2^24, `OpenHashMap` calculates incorrect index of value in `_values` array.

I've also added a size check in `rehash()`, so that it fails instead of reporting invalid item indices.

Author: Vyacheslav Baranov <slavik.baranov@gmail.com>

Closes #6763 from SlavikBaranov/SPARK-8309 and squashes the following commits:

8557445 [Vyacheslav Baranov] Resolved review comments
4d5b954 [Vyacheslav Baranov] Resolved review comments
eaf1e68 [Vyacheslav Baranov] Fixed failing test
f9284fd [Vyacheslav Baranov] Resolved review comments
3920656 [Vyacheslav Baranov] SPARK-8309: Support for more than 12M items in OpenHashMap