Fix support for "aws/aws-sdk-php:^3.0"

[phansys]

Subject

Fix support for "aws/aws-sdk-php:^3.0".

I am targeting this branch, because these changes respect BC.

Related to #1018.

Changelog

### Fixed
- Fixed calls to deprecated method `AwsClient::factory()` when using aws/aws-sdk-php:^3.0;
- Fixed passing required arguments to "sonata.media.cdn.cloudfront" service when using aws/aws-sdk-php:^3.0;
- Fixed respecting "sonata_media.filesystem.s3.region", "sonata_media.filesystem.s3.version" and "sonata_media.filesystem.s3.endpoint" configuration nodes when using aws/aws-sdk-php:^2.0.

### Deprecated
- Deprecated "sonata_media.filesystem.s3.sdk_version" configuration node.

To do

• Deprecate sonata_media.filesystem.s3.sdk_version configuration node, since there is no way to install "aws/aws-sdk-php" 2.x and 3.x at the same time (this probably was added to switch between version 1.x and 2.x, since 1.x was provided by a different package).
• Add new CloudFront configuration options required in v3.x (region, version, etc).
• Update the documentation;
• Fix the arguments passed to CloudFrontClient::createInvalidation() when using aws/aws-sdk-php:^3.0.

[core23]

Please line break this

[wbloszyk]

Technicly it is the same, but better see diffrence between both versions.

Suggested change

	$arguments['InvalidationBatch'] = $invalidationBatch;
	$arguments += ['InvalidationBatch' => $invalidationBatch];

[wbloszyk]

Suggested change

	// @todo: Remove the following check and the `else` block when support for aws/aws-sdk-php < 3.0 is dropped.
	if (class_exists(Sdk::class)) {
	// AWS v3.x.
	$config['credentials'] = [
	'key' => $this->region,
	'secret' => $this->version,
	];
	$this->client = new CloudFrontClient($config);
	} else {
	// AWS v2.x.
	$config['key'] = $this->region;
	$config['secret'] = $this->version;
	$this->client = CloudFrontClient::factory($config);
	}
	$keysConfig = [
	'key' => $this->region,
	'secret' => $this->version,
	];
	// @todo: Remove the following check and the `else` block when support for aws/aws-sdk-php < 3.0 is dropped.
	if (class_exists(Sdk::class)) {
	// AWS v3.x.
	$this->client = new CloudFrontClient($config+['credentials' => $keysConfig]);
	} else {
	// AWS v2.x.
	$this->client = CloudFrontClient::factory($config+$keysConfig);
	}

[jordisala1991]

Thank you @phansys