Add ReturnTypeWillChange to ReflectionEmbeddedProperty

[derrabus]

PHP 8.1 will introduce a process to add return types to internal methods, see https://wiki.php.net/rfc/internal_method_return_types

• Follows Add ReturnTypeWillChange to PDO implementations dbal#4662
• Follows Add ReturnTypeWillChange to extended reflection classes persistence#189

This library extends ReflectionProperty and overrides public methods that are affected by this change. PHP 8.1 triggers deprecation warnings unless we declare that a future version of this library will add these return types as well. We can do so by adding the ReturnTypeWillChange attribute to those methods.

This PR suggests to do just that because adding the actual return types would break code that extends our classes. A future 3.0 release could add the actual return types.

[derrabus]

The PHP CodeSniffer errors seem to be false positives.

edit: Reported as slevomat/coding-standard#1233

[greg0ire]

@derrabus let's add an ignore rule with the link above then? Or is the plan to wait for an upstream fix?

[derrabus]

let's add an ignore rule with the link above then?

Done.

[greg0ire]

Thanks @derrabus !