Replace current test image creation with more elegant PSR compliant solution

[nmeri17]

This refers to the methods covered here: https://github.com/nmeri17/Tilwa/blob/1a2afe17993353473dfa5805b639928b261c31df/nmeri/tilwa/src/Testing/Condiments/FilesystemCleaner.php#L136-L177

It works but there's still room for improvement. The two alternatives I've tried (Nyholm\Psr7 and Laminas\Diactoros) have scant documentation for this purpose or the specific classes. The code suggests it won't serve my purpose. A modified version of saveFakeImage will look like this:

protected function saveFakeImage (string $fileName, int $width, int $height, int $expectedSize = 100):UploadedFile {

	$stream = $this->getImageStream($width, $height);

	while ($stream->getSize() *1024 < $expectedSize)

		$stream->write($this->getImageStream($width, $height));

	return UploadedFileFactory::createUploadedFile($stream, $expectedSize, 0, $fileName);
}

private function getImageStream (int $width, int $height):StreamInterface {

	$imageResource = imagecreatetruecolor($width, $height);

	$stream = StreamFactory::createStream($imageResource); // this is the line of interest

	imagedestroy($imageResource);

	return $stream;
}

On the line of interest, Laminas\Diactoros creates stream in read only mode. This prevents saveFakeImage from writing to it. On the other hand, Nyholm\Psr7 is gracious enough to open stream in read/write mode. Sadly, it clears stream size after it's being written to, preventing incremental addition by saveFakeImage

Aside the fact that this looks cleaner to the present alternative, there's no creating and deletion of dummy images written to disk, meaning it'll perform better. It also means we won't need the extra Symfony bridge to create UploadedFileInterface instances applicable in both test and live environments