Allow full usage of subquery from clause

[beikov]

Currently our FromBuilder only supports the usage of entities, but JPQL subqueries may also contain other constructs.

A derived_path_expression is a reference to some association of a variable defined by the parent query. The following example should illustrate how that can look.

SELECT a FROM A a WHERE EXISTS(SELECT 1 FROM a.collection)

Note that the non-terminals derived_collection_member_declaration and collection_member_expression IMO provide the same functionality like derived_path_expression which is why I'd opt for just implementing it that way.