[JVM] Improve debug step behavior around lambdas.

- Add tests to clarify problematic behavior
- Avoid line numbers on return instructions of lambdas without explicit returns

compiler/backend/src/org/jetbrains/kotlin/codegen/ExpressionCodegen.java

@@ -1759,8 +1759,7 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
         if (!endsWithReturn(expr)) {
             if (isLambdaVoidBody(expr, typeForExpression)) {
                 markLineNumber((KtFunctionLiteral) expr.getParent(), true);
-            }
-            else {
+            } else if (!isLambdaBody(expr)){
                 markLineNumber(expr, true);
             }
 
@@ -1782,13 +1781,14 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
     }
 
     private static boolean isLambdaVoidBody(@NotNull KtElement bodyExpression, @NotNull Type returnType) {
+        return isLambdaBody(bodyExpression) && Type.VOID_TYPE.equals(returnType);
+    }
+
+    private static boolean isLambdaBody(@NotNull KtElement bodyExpression) {
         if (bodyExpression instanceof KtBlockExpression) {
             PsiElement parent = bodyExpression.getParent();
-            if (parent instanceof KtFunctionLiteral) {
-                return Type.VOID_TYPE.equals(returnType);
-            }
+            return parent instanceof KtFunctionLiteral;
         }
-
         return false;
     }