Breaking: #75645 - Doctrine: migrate ext:backend/Tree

See Issue #75645

Description

This patch changes all database related functions to use the new Doctrine database API. The method getDatabaseConnection() has been removed.

Impact

Calls to the method AbstractTreeView::getDataInit() will now return Statement objects. All other AbstractTreeView::getData* methods now expect such a Statement object instead of a SQL resource.

Affected Installations

All installations using TreeViews extending the AbstractTreeView.

Migration

Migrate all calls that work with the result Statement from TreeView to be able to handle Statement objects.