Replace the current toolbar implementation with the new PageHeader component on the (rails) admin pages

* [ ] Overview
* [x] Users and permissions, will be done in the scope <mention class="mention" data-id="50109" data-type="work_package" data-text="#50109">#50109</mention>&nbsp;
* [x] (and child pages)
* [ ] Work Begin of the insertionpackages, will be done in the scope of #56585End of the insertion Begin of the deletion packagesEnd of the deletion
* [ ] (and child pages)
* [ ] Begin of the insertionProjects, will be done in the scope of #56586End of the insertion Begin of the deletion ProjectsEnd of the deletion
* [ ] (and child pages)
* [ ] Custom fields
* [ ] Attribute help texts
* [ ] Enumerations
* [ ] Calendars and Begin of the insertiondates, will be done in the scope of #56587End of the insertion Begin of the deletion datesEnd of the deletion
* [ ] (and child pages)
* [ ] System Begin of the insertionsettings, will be done in the scope of #56587End of the insertion Begin of the deletion settingsEnd of the deletion
* [ ] (and child pages)
* [ ] Email
* [ ] (and child pages)
* [ ] API Begin of the insertionand webhooks, will be done in the scope of #56587End of the insertion
* [ ] (and child pages)
* [ ] Authentication
* [ ] (and child pages)
* [ ] Announcements
* [ ] Design
* [ ] Colors
* [ ] Enterprise edition
* [x] Time and costs, will be done in the scope Begin of the insertion#50109End of the insertion Begin of the deletion <mention class="mention" data-id="50109" data-type="work_package" data-text="#50109">#50109</mention>End of the deletion
* [x] (and child pages)
* [ ] Backlogs
* [ ] (and child pages)
* [ ] Github Begin of the insertionintegration, will be done in the scope of #56587End of the insertion Begin of the deletion integrationEnd of the deletion
* [ ] Slack integration
* [x] Storages
* [x] (and child pages)
* [ ] Plugins
* [ ] backup
* [ ] Information