Rewrite DCA image size options to service

[aschempp]

Old:

'imageSize' => array(
    'inputType' => 'imageSize',
    'options' => \System::getImageSizes(),
),

Old:

'imageSize' => array(
    'inputType' => 'imageSize',
    'options' => \Contao\System::getContainer()->get('contao.image.sizes')->getAllOptions(),
),

[zoglo]

Stumbled across this issue and tried to implement this when I found out that the image size options were dropped due to the 'imageSize' widget adding the options now.

Is this conversion still necessary or could we just drop the 'options' completely nowadays?