IC: Forbid inner classes inside inline classes

#KT-43067 Fixed

compiler/testData/diagnostics/tests/inlineClasses/innerClassInsideInlineClass.fir.kt

@@ -0,0 +1,8 @@
+// !LANGUAGE: +InlineClasses
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+
+inline class Foo(val x: Int) {
+    inner class InnerC
+    inner object InnerO
+    inner interface InnerI
+}

compiler/testData/diagnostics/tests/inlineClasses/innerClassInsideInlineClass.kt

@@ -0,0 +1,8 @@
+// !LANGUAGE: +InlineClasses
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+
+inline class Foo(val x: Int) {
+    <!INNER_CLASS_INSIDE_INLINE_CLASS!>inner<!> class InnerC
+    <!WRONG_MODIFIER_TARGET!>inner<!> object InnerO
+    <!WRONG_MODIFIER_TARGET!>inner<!> interface InnerI
+}

compiler/testData/diagnostics/tests/inlineClasses/innerClassInsideInlineClass.txt

@@ -0,0 +1,29 @@
+package
+
+public final inline class Foo {
+    public constructor Foo(/*0*/ x: kotlin.Int)
+    public final val x: kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+
+    public final inner class InnerC {
+        public constructor InnerC()
+        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
+    }
+
+    public interface InnerI {
+        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
+    }
+
+    public object InnerO {
+        private constructor InnerO()
+        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
+    }
+}