Convert "lift return / assignment" intentions into a single inspection

Also includes minor test fix, related to KT-14900

idea/testData/inspectionsLocal/liftOut/whenToAssignment/simpleWhenWithoutTerminatingAssignment.kt

@@ -0,0 +1,19 @@
+// PROBLEM: none
+fun <T> doSomething(a: T) {}
+
+fun test(n: Int): String {
+    var res: String
+
+    <caret>when (n) {
+            1 -> {
+                doSomething("***")
+                res = "one"
+            }
+            else -> {
+                res = "two"
+                doSomething("***")
+            }
+    }
+
+    return res
+}