[!!!][TASK] Clean up Environment after HTTP refactoring
With the HTTP foundation quite some things from Environment have become
obsolete. The class and it's "users" are adjusted in this change.
The following methods are removed from Environment (check Http\Request
to see if a method you need is available there) with this change:
Most of those were marked as public API, but we still decided to drop
them, as their use cases were only guesswork.
For some things that used to be available, access to the current request
is now needed. For this, getHttpRequest() was added to the new
HttpRequestHandlerInterface, which returns the current HttpRequest.