This commit includes three changes:
1. 'EnhancedNullability' is no more set for declaration types
2. It is no more used for conversion types in translator
3. Translator inserts implicit not-null cast only when enhanced type is cast to not-null type.
See KT-35849.
1. When expected lambda return type is a type parameter, don't generate
introduce implicit casts (even if the corresponding type parameter has
an upper bound that would otherwise require such cast).
2. Do not generate implicit null check for lambda return value of
@EnhancedNullability type.
Mikhail Glukhikh