GH-470: [Vector] Fix ListViewVector.getElementEndIndex(index) method

[axreldable]

What's Changed

First commit changes logic:

• The PR fixes a bug in the ListViewVector.getElementEndIndex(index) method .

Before:

public int getElementEndIndex(int index) {
  return sizeBuffer.getInt(index * OFFSET_WIDTH);
}

After:

public int getElementEndIndex(int index) {
  return offsetBuffer.getInt(index * OFFSET_WIDTH) + sizeBuffer.getInt(index * SIZE_WIDTH);
}

Second commit doesn't change logic:

• Fixes a bug of usage sizeBuffer with OFFSET_WIDTH (hashCode method) and offsetBuffer with SIZE_WIDTH (setSize method). It doesn't introduce real changes in the logic as OFFSET_WIDTH == SIZE_WIDTH == 4

• Plus small refactoring of ListViewVector to avoid code duplication and similar issues in the future.

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It's a bug fix.

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Closes #470.

[axreldable]

Please add the bug-fix label.