Tests if type has trivial default constructor.
An instance of the type predicate holds true if the type Ty is a class that has a trivial constructor, otherwise it holds false.
A default constructor for a class Ty is trivial if:
it is an implicitly declared default constructor
the class Ty has no virtual functions
the class Ty has no virtual bases
all the direct bases of the class Ty have trivial constructors
the classes of all the non-static data members of class type have trivial constructors
the classes of all the non-static data members of type array of class have trivial constructors