Fix EZP-22045: As a developer, I want user login to be fully handled by Symfony stack

**DO NOT MERGE**

https://jira.ez.no/browse/EZP-22045

Depends on https://github.com/ezsystems/ezpublish-kernel/pull/656 and https://github.com/ezsystems/ezpublish-community/pull/87

## TASKS
* [x] Update links for login/logout
* [x] Update siteaccess configuration for default layout
* [x] Override base `login.html.twig` to match demo layout