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

Also includes minor test fix, related to KT-14900

idea/testData/inspectionsLocal/liftOut/whenToAssignment/innerWhenTransformed.kt.after

@@ -0,0 +1,23 @@
+fun <T> doSomething(a: T) {}
+
+fun test(n: Int): String {
+    var res: String
+
+    if (3 > 2) {
+        <caret>res = when (n) {
+            1 -> {
+                doSomething("***")
+                "one"
+            }
+            else -> {
+                doSomething("***")
+                "two"
+            }
+        }
+    } else {
+        doSomething("***")
+        res = "???"
+    }
+
+    return res
+}