Refine 'handleResult' calls generation within coroutines

Before this change everything works just fine for 'handleResult' methods
accepting non-Unit parameters

For other cases the same coercion-to-unit strategy is in plain lambdas:
- if last statement is not Unit type, execute it, pop from the stack, then put Unit instance
- for 'return@label' (no expression) just put Unit on the stack

 #KT-13531 Fixed

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -4324,6 +4324,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/codegen/box/coroutines"), Pattern.compile("^(.+)\\.kt$"), true);
         }
 
+        @TestMetadata("coercionToUnit.kt")
+        public void testCoercionToUnit() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/coroutines/coercionToUnit.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("controllerAccessFromInnerLambda.kt")
         public void testControllerAccessFromInnerLambda() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/coroutines/controllerAccessFromInnerLambda.kt");