feature #25836 [HttpKernel] Make session-related services extra-lazy (nicolas-grekas)

This PR was merged into the 4.1-dev branch.

Discussion
----------

[HttpKernel] Make session-related services extra-lazy

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Commits
-------

5f535581b9 [HttpKernel] Make session-related services extra-lazy

Author: fabpot

Resources/config/session.xml

@@ -63,13 +63,14 @@
                     <tag name="container.service_locator" />
                     <argument type="collection">
                         <argument key="session" type="service" id="session" on-invalid="ignore" />
+                        <argument key="initialized_session" type="service" id="session" on-invalid="ignore_uninitialized" />
                     </argument>
                 </service>
             </argument>
         </service>
 
         <service id="session.save_listener" class="Symfony\Component\HttpKernel\EventListener\SaveSessionListener">
-            <tag name="kernel.event_subscriber" />
+            <deprecated>The "%service_id%" service is deprecated since Symfony 4.1 and will be removed in 5.0. Use the "session_listener" service instead.</deprecated>
         </service>
 
         <!-- for BC -->