Introduce "Add missing 'class' keyword" intention

#KT-14884 Fixed

idea/testData/intentions/addMissingClassKeyword/.intention

@@ -0,0 +1 @@
+org.jetbrains.kotlin.idea.intentions.AddMissingClassKeywordIntention

idea/testData/intentions/addMissingClassKeyword/abstract.kt

@@ -0,0 +1,5 @@
+// IS_APPLICABLE: false
+// DISABLE-ERRORS
+abstract <caret>Foo {
+    abstract fun foo()
+}

idea/testData/intentions/addMissingClassKeyword/annottion.kt

@@ -0,0 +1 @@
+annotation <caret>Foo

idea/testData/intentions/addMissingClassKeyword/annottion.kt.after

@@ -0,0 +1 @@
+annotation class Foo

idea/testData/intentions/addMissingClassKeyword/data.kt

@@ -0,0 +1,7 @@
+// DISABLE-ERRORS
+annotation class Ann
+
+@Ann
+private data <caret>Foo(val s: String) {
+    fun foo() {}
+}

idea/testData/intentions/addMissingClassKeyword/data.kt.after

@@ -0,0 +1,7 @@
+// DISABLE-ERRORS
+annotation class Ann
+
+@Ann
+private data class Foo(val s: String) {
+    fun foo() {}
+}

idea/testData/intentions/addMissingClassKeyword/dataHasClassKeyword.kt

@@ -0,0 +1,2 @@
+// IS_APPLICABLE: false
+private data class <caret>Foo(val s: String)

idea/testData/intentions/addMissingClassKeyword/enum.kt

@@ -0,0 +1,3 @@
+enum Foo<caret>(val s: String) {
+    A("a"), B("b")
+}

idea/testData/intentions/addMissingClassKeyword/enum.kt.after

@@ -0,0 +1,3 @@
+enum class Foo(val s: String) {
+    A("a"), B("b")
+}

idea/testData/intentions/addMissingClassKeyword/enumHasClassKeyword.kt

@@ -0,0 +1,4 @@
+// IS_APPLICABLE: false
+enum class <caret>Foo(val s: String) {
+    A("a"), B("b")
+}

idea/testData/intentions/addMissingClassKeyword/inner.kt

@@ -0,0 +1,3 @@
+class C {
+    inner <caret>Foo
+}

idea/testData/intentions/addMissingClassKeyword/inner.kt.after

@@ -0,0 +1,3 @@
+class C {
+    inner class Foo
+}

idea/testData/intentions/addMissingClassKeyword/sealed.kt

@@ -0,0 +1,4 @@
+// DISABLE-ERRORS
+sealed <caret>Foo {
+    abstract fun foo()
+}

idea/testData/intentions/addMissingClassKeyword/sealed.kt.after

@@ -0,0 +1,4 @@
+// DISABLE-ERRORS
+sealed class Foo {
+    abstract fun foo()
+}