Support query builder beginning methods from `gedmo/doctrine-extensions`

[gharlan]

I don't know if it's out of scope here, but it would be nice, if the query builder methods from https://github.com/doctrine-extensions/DoctrineExtensions could be supported out of the box (avoiding doctrine.queryBuilderDynamic).

The methods are:

• AbstractTreeRepository::getRootNodesQueryBuilder
• AbstractTreeRepository::getNodesHierarchyQueryBuilder
• ClosureTreeRepository::childrenQueryBuilder
• MaterializedPathRepository::getTreeQueryBuilder
• MaterializedPathRepository::getPathQueryBuilder
• NestedTreeRepository::getPathQueryBuilder
• NestedTreeRepository::childrenQueryBuilder
• SortableRepository::getBySortableGroupsQueryBuilder

[janedbal]

This extension needs to know what is happening to the DQL AST inside those methods in order to support them properly. Looking at the logic there, it might not be as easy.

[ondrejmirtes]

We could fix this by hardcoding the logic of these methods here in this extension.