[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/testData/codegen/boxInline/smap/defaultLambda/inlinInDefault2.kt

@@ -133,7 +133,6 @@ test/_1Kt$lParams$1
 71#2,2:12
 30#2:15
 51#3:14
-69#3:16
 *E
 *S KotlinDebug
 *F
@@ -144,5 +143,4 @@ _2Kt
 6#1,2:12
 6#1:15
 6#1:14
-6#1:16
 *E