EZP-22193: Make the website toolbar available from a twig pagelayout

> **Work in progress**
> JIRA issue: http://jira.ez.no/browse/EZP-22193
> Requires ezsystems/ezpublish-kernel#755

Uses a new controller (`ezpublish_legacy.website_toolbar.controller`) that renders the legacy websitetoolbar template.

### Tasks
- [x] Load `websitetoolbar.css` without using assetic (to work around relative asset path issues)
- [ ] Only load `websitetoolbar.css` if the toolbar is actually shown (requires policy check)