fix: [DatePicker] Construct new moment objects with custom dateFormat

[skvale]

Description

Without these changes this test

test('provide ISO-8601 format date with custom dateFormat in props', () => {
  wrapper = mount(<DatePicker dateFormat='DD-MM-YYYY' defaultValue='01-06-2020' />);
  expect(wrapper.state('isoFormattedDate')).toEqual('2020-06-01');
});

would fail with

Expected: "2020-06-01"
Received: "2020-01-06"

where the isoFormattedDate was created with switched month and day values

And this test

        test('should format isoFormattedDate when a custom dateFormat is passed in props', () => {
            const blur = jest.fn();
            const element = mount(<DatePicker
                dateFormat='DD-MM-YYYY'
                defaultValue='01-06-2020'
                onBlur={blur} />).find('input[type="text"]');
            element.find('input[type="text"]').simulate('click');
            element.find('input[type="text"]').simulate('change', { target: { value: '30-06-2020' } });
            element.find('input[type="text"]').simulate('blur');

            expect(blur).toHaveBeenCalledTimes(1);
            expect(blur).toHaveBeenCalledWith(expect.objectContaining({
                isoFormattedDate: '2020-06-30'
            }));
        });

would fail with

Expected: ObjectContaining {"isoFormattedDate": "2020-06-30"}
Received: {"date": "2020-06-30T05:00:00.000Z", "formattedDate": "30-06-2020", "isoFormattedDate": "Invalid date"}

where it would just fail to create the isoFormattedDate

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[jbadan]

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