Improve: add more cases for MoveVariableDeclarationIntoWhen

#KT-30499 Fixed

idea/testData/inspectionsLocal/moveVariableDeclarationIntoWhen/inBinaryExpression.kt

@@ -0,0 +1,9 @@
+fun test() = true
+
+fun foo(): Int {
+    val a<caret> = test()
+    return when (a) {
+        true -> 42
+        else -> null
+    } ?: 55
+}