[breadcrumbs] Small breadcrumb components refactoring * use `open_breadcrumbs` and `close_breadcrumbs` methods where applicable in the BreadCrumbEntityVComponent hierarchy * include the first separator related code in `open_breadcrumbs` to avoid code duplication Closes #3223911.

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Add some entities

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As manager, you can access to entity creation forms by using the `site management`_ page.

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.. _`site management`: manage

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As regular user, the index page or the action box may propose some links to create entities according to the context.

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