Session Storage methods are incompatible with HttpFoundation 6.*

[liviucmg]

Some methods are missing the return types, so we're getting the following errors:

In VirtualSessionStorage.php line 54:
                                                                                                                                                                                                                 
  Compile Error: Declaration of Ratchet\Session\Storage\VirtualSessionStorage::regenerate($destroy = false, $lifetime = null) must be compatible with Symfony\Component\HttpFoundation\Session\Storage\NativeSe  
  ssionStorage::regenerate(bool $destroy = false, ?int $lifetime = null): bool 

In VirtualProxy.php line 29:
                                                                                                                                                                                                   
  Compile Error: Declaration of Ratchet\Session\Storage\Proxy\VirtualProxy::getId() must be compatible with Symfony\Component\HttpFoundation\Session\Storage\Proxy\AbstractProxy::getId(): string  

We're currently using symfony/http-foundation v6.1.1.

The fixes are straightforward, and I will submit a PR shortly.

Related to #963.