[FIR] Change API for generating nested classes from plugins

`FirDeclarationGenerationExtension.generateClassLikeDeclaration` was split
  into two functions: one for generating top level classes, and one for
  nested classes. Such change reduces verbosity and error-proness of
  this extension and also allows to smoothly run plugins on local classes

^KT-55248 Fixed

plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirBlackBoxTestGenerated.java

@@ -265,6 +265,12 @@ public class SerializationFirBlackBoxTestGenerated extends AbstractSerialization
             runTest("plugins/kotlinx-serialization/testData/firMembers/serializableWithCompanion.kt");
         }
 
+        @Test
+        @TestMetadata("serializerInLocalClass.kt")
+        public void testSerializerInLocalClass() throws Exception {
+            runTest("plugins/kotlinx-serialization/testData/firMembers/serializerInLocalClass.kt");
+        }
+
         @Test
         @TestMetadata("serializerViaCompanion.kt")
         public void testSerializerViaCompanion() throws Exception {

plugins/kotlinx-serialization/tests-gen/org/jetbrains/kotlinx/serialization/runners/SerializationFirDiagnosticTestGenerated.java

@@ -240,6 +240,12 @@ public class SerializationFirDiagnosticTestGenerated extends AbstractSerializati
             runTest("plugins/kotlinx-serialization/testData/firMembers/serializableWithCompanion.kt");
         }
 
+        @Test
+        @TestMetadata("serializerInLocalClass.kt")
+        public void testSerializerInLocalClass() throws Exception {
+            runTest("plugins/kotlinx-serialization/testData/firMembers/serializerInLocalClass.kt");
+        }
+
         @Test
         @TestMetadata("serializerViaCompanion.kt")
         public void testSerializerViaCompanion() throws Exception {