[entity] upgrade fetch_[unrelated_]order to benefit from changes introduced in 3.14 (closes #1942758)

of rql generation parts of the ORM now based on rql syntax tree. This allows more powerful and
flexible sort control by giving them the syntax tree instead of manipulating string.

Also:

* prefix new methods by 'cw_'

* fix cases that currently crash in 3.14 due to the refactoring