Add inspection: Refactor sealed sub-class to object #KT-20305 Fixed

idea/testData/inspections/sealedSubClassCanBeObject/sealed.kt

@@ -0,0 +1,47 @@
+sealed class Sealed {
+    open class OpenSubSealedNestedNoChild() : Sealed()
+
+    open class SubSealedNestedWithChild  : Sealed()
+
+    class SubSealedNestedChild() : SubSealedNestedWithChild()
+
+    final class FinalSubSealedNested() : Sealed()
+
+    class SubSealedNested() : Sealed()
+}
+
+class SubSealedParentheses() : Sealed()
+
+class SubSealedNoParentheses : Sealed()
+
+open class SubSealedWithChild : Sealed()
+
+class SubSealedChild : SubSealedWithChild()
+
+class SubSealedParameters(val value : String) : Sealed()
+
+object SubSealedObject() : Sealed()
+
+class SubSealedObjectWithPrimaryConstructor(parameter: String) : Sealed()
+
+class SubSealedObjectWithSecondaryConstructor() : Sealed() {
+    constructor(parameter: String): this()
+}
+
+object AlreadyObject: Sealed()
+
+class SubSealedWithCompanion: Sealed() {
+    companion object
+}
+
+class SubSealedWithInner: Sealed() {
+    inner class Inner
+}
+
+class SubSealedWithNested: Sealed() {
+    class Nested
+}
+
+class SubSealedWithFunction: Sealed() {
+    fun internalFunction() { }
+}