[KPM] Make KotlinSerializableExternalModelSerializer private

KT-51262
KT-51220

libraries/tools/binary-compatibility-validator/reference-public-api/kotlin-gradle-plugin-idea.txt

@@ -50,14 +50,6 @@ public abstract class org/jetbrains/kotlin/gradle/kpm/KotlinMutableExternalModel
 	public abstract fun set (Lorg/jetbrains/kotlin/gradle/kpm/KotlinExternalModelKey;Ljava/lang/Object;)V
 }
 
-public final class org/jetbrains/kotlin/gradle/kpm/KotlinSerializableExternalModelSerializer : org/jetbrains/kotlin/gradle/kpm/KotlinExternalModelSerializer {
-	public fun <init> (Ljava/lang/Class;)V
-	public fun deserialize ([B)Ljava/io/Serializable;
-	public synthetic fun deserialize ([B)Ljava/lang/Object;
-	public fun serialize (Ljava/io/Serializable;)[B
-	public synthetic fun serialize (Ljava/lang/Object;)[B
-}
-
 public abstract interface class org/jetbrains/kotlin/gradle/kpm/idea/IdeaKotlinFragment : java/io/Serializable {
 	public abstract fun getDependencies ()Ljava/util/Collection;
 	public abstract fun getDirectRefinesDependencies ()Ljava/util/Collection;

libraries/tools/kotlin-gradle-plugin-idea/src/main/kotlin/org/jetbrains/kotlin/gradle/kpm/KotlinExternalModelSerializer.kt

@@ -15,12 +15,14 @@ interface KotlinExternalModelSerializer<T : Any> {
     @InternalKotlinGradlePluginApi
     companion object {
         inline fun <reified T : Serializable> serializable(): KotlinExternalModelSerializer<T> =
-            KotlinSerializableExternalModelSerializer(T::class.java)
+            serializable(T::class.java)
+
+        fun <T : Serializable> serializable(clazz: Class<T>): KotlinExternalModelSerializer<T> =
+            KotlinSerializableExternalModelSerializer(clazz)
     }
 }
 
-@PublishedApi
-internal class KotlinSerializableExternalModelSerializer<T : Serializable>(
+private class KotlinSerializableExternalModelSerializer<T : Serializable>(
     private val clazz: Class<T>
 ) : KotlinExternalModelSerializer<T> {
     override fun serialize(value: T): ByteArray {