Replace return with 'if'/'when': don't drop return label

#KT-30414 Fixed

idea/testData/intentions/branched/unfolding/returnToIf/labeledReturn.kt

@@ -0,0 +1,10 @@
+// WITH_RUNTIME
+fun main() {
+    run label@{
+        <caret>return@label if (true) {
+            42
+        } else {
+            42
+        }
+    }
+}

idea/testData/intentions/branched/unfolding/returnToIf/labeledReturn.kt.after

@@ -0,0 +1,10 @@
+// WITH_RUNTIME
+fun main() {
+    run label@{
+        <caret>if (true) {
+            return@label 42
+        } else {
+            return@label 42
+        }
+    }
+}

idea/testData/intentions/branched/unfolding/returnToWhen/labeledReturn.kt

@@ -0,0 +1,10 @@
+// WITH_RUNTIME
+fun main() {
+    run label@{
+        <caret>return@label when {
+            true ->
+                42
+            else -> 42
+        }
+    }
+}

idea/testData/intentions/branched/unfolding/returnToWhen/labeledReturn.kt.after

@@ -0,0 +1,10 @@
+// WITH_RUNTIME
+fun main() {
+    run label@{
+        <caret>when {
+            true ->
+                return@label 42
+            else -> return@label 42
+        }
+    }
+}