Fix serialization of type parameters inner generic class

The call to `createTopLevel` instead of `create` (which creates
serializers for outer classes properly, with correct type parameter
contexts) caused MetadataSerializer to write type parameter metadata
incorrectly.  For example, in the following case:

    class A<E> {
        inner class B<T, E> { ... }
    }

A's type parameter E would get id 0, and B's type parameters T and E
would get ids 0 and 1. This is a problem because ids are supposed to be
unique for each class including its outer classes, and deserializer,
decompiler and stub builder rely on this assumption.

JVM metadata is unaffected because `create` is called correctly there,
see MemberCodegen#generateKotlinClassMetadataAnnotation

 #KT-24944 Fixed

compiler/testData/multiplatform/innerGenericClass/common.kt

@@ -0,0 +1,9 @@
+class A<E> {
+    inner class B<T, E> {
+        fun getAE() = this@A.getAE()
+        fun getBT(): T? = null
+        fun getBE(): E? = null
+    }
+
+    fun getAE(): E? = null
+}