PSI2IR: Unify behavior for lambda return values with old back-end

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.

compiler/tests/org/jetbrains/kotlin/ir/IrTextTestCaseGenerated.java

@@ -1086,6 +1086,11 @@ public class IrTextTestCaseGenerated extends AbstractIrTextTestCase {
             runTest("compiler/testData/ir/irText/expressions/multipleThisReferences.kt");
         }
 
+        @TestMetadata("nullCheckOnGenericLambdaReturn.kt")
+        public void testNullCheckOnGenericLambdaReturn() throws Exception {
+            runTest("compiler/testData/ir/irText/expressions/nullCheckOnGenericLambdaReturn.kt");
+        }
+
         @TestMetadata("nullCheckOnLambdaReturn.kt")
         public void testNullCheckOnLambdaReturn() throws Exception {
             runTest("compiler/testData/ir/irText/expressions/nullCheckOnLambdaReturn.kt");