Report warning on modifier list of primary ctor unless 'constructor' keyword specified

compiler/testData/diagnostics/tests/modifiers/primaryConstructorMissingKeyword.kt

@@ -0,0 +1,9 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+annotation class Ann(val x: Int = 1)
+class A <!MISSING_CONSTRUCTOR_KEYWORD!>private<!> (val x: Int) {
+inner class B <!MISSING_CONSTRUCTOR_KEYWORD!>Ann(2)<!> (val y: Int)
+
+fun foo() {
+    class C <!MISSING_CONSTRUCTOR_KEYWORD!>private @Ann(3)<!> (args: Int)
+    }
+}

compiler/testData/diagnostics/tests/modifiers/primaryConstructorMissingKeyword.txt

@@ -0,0 +1,26 @@
+package
+
+internal final class A {
+    private constructor A(/*0*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    internal final fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal final inner class B {
+        Ann(x = IntegerValueType(2): IntegerValueType(2)) public constructor B(/*0*/ y: kotlin.Int)
+        internal final val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}
+
+internal final annotation class Ann : kotlin.Annotation {
+    public constructor Ann(/*0*/ x: kotlin.Int = ...)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}