todo comment added
refactoring

use method instead of its realisation, inline method
made delegated property resolver a component

from DelegatedPropertyUtils
moved method
resolve delegated expression always using completer
do not add NO_EXPECTED_TYPE as a subtype constraint to constraint system

fixed exception from EA
refactoring: added hasOnlyErrorsFromPosition(ConstraintPosition)
to use it for errors from completer as well
added comment

about the case when nullable type variable is constrained by not nullable type