Change augmentation field visibility to default

In any builder, agumentation field is private. Builder contains innerclass ...Impl that is accessing this field, resulting in inefficient behaviour:

This method of an inner class reads from or writes to a private member variable of the owning class. The compiler must generate a special method to access this private member, causing this to be less efficient. Relaxing the protection of the member variable will allow the compiler to treat this as a normal access.