Adjust the "preserve metadata" logic

[leofeyer]

Fixes #6205

One thing is still bothering me, though: If I use a predefined image size, the preserveMetadata key stores the formats to preserve.

contao/core-bundle/tests/Image/ImageFactoryTest.php

Lines 329 to 344 in c19feca

	$predefinedSizes = [
	'foobar' => [
	'width' => 100,
	'height' => 200,
	'resizeMode' => ResizeConfiguration::MODE_BOX,
	'zoom' => 50,
	'imagineOptions' => [
	'jpeg_quality' => 77,
	'jxl_quality' => 66,
	],
	'preserveMetadata' => [
	ExifFormat::NAME => [],
	IptcFormat::NAME => ['2#116', '2#080'],
	],
	],
	];

In the tl_image_size table, however, the preserveMetadata key stores whether to overwrite the formats and the metadata key actually holds the formats to preserve.

contao/core-bundle/tests/Image/ImageFactoryTest.php

Lines 256 to 267 in c19feca

	$imageSizeProperties = [
	'width' => 100,
	'height' => 200,
	'resizeMode' => ResizeConfiguration::MODE_BOX,
	'zoom' => 50,
	'preserveMetadata' => true,
	'imageQuality' => 77,
	'metadata' => serialize([
	serialize([ExifFormat::NAME => ExifFormat::DEFAULT_PRESERVE_KEYS]),
	serialize([IptcFormat::NAME => IptcFormat::DEFAULT_PRESERVE_KEYS]),
	]),
	];

Is this what we want?