[Tree][MaterializedPath] Fix getChildrenQueryBuilder method for node defined without end separator

This PR fixing getChildrenQueyrBuilder method for materialized path node without end separator.
I added getChildrenForEntityWithTrimmedSeparators test which should covers most of issues.
Basically with such options ` @Gedmo\TreePath(appendId=false, startsWithSeparator=false, endsWithSeparator=false)` includeNode did not work.