[FIR] Get rid of FirProvidedDeclarationsForMetadataService.getProvidedNestedClassifiers

It's now impossible to add new classes to metadata, because this
  functionality is not implemented in IrGeneratedDeclarationsRegistrar
  and FirDeclarationsForMetadataProviderExtension is removed

compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirElementSerializer.kt

@@ -380,7 +380,6 @@ class FirElementSerializer private constructor(
      * Order of nested classifiers:
      *   - declared classifiers in declaration order
      *   - generated classifiers in sorted order
-     *   - provided classifiers in sorted order
      */
     fun computeNestedClassifiersForClass(classSymbol: FirClassSymbol<*>): List<FirClassifierSymbol<*>> {
         val scope = session.nestedClassifierScope(classSymbol.fir) ?: return emptyList()
@@ -391,11 +390,6 @@ class FirElementSerializer private constructor(
                 .partition { it in indexByDeclaration }
             declared.sortedBy { indexByDeclaration.getValue(it) }.mapTo(this) { it.symbol }
             nonDeclared.sortedWith(FirMemberDeclarationComparator).mapTo(this) { it.symbol }
-
-            providedDeclarationsService.getProvidedNestedClassifiers(classSymbol, scopeSession)
-                .map { it.fir }
-                .sortedWith(FirMemberDeclarationComparator)
-                .mapTo(this) { it.symbol }
         }
     }
 

compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirProvidedDeclarationsForMetadataService.kt

@@ -66,7 +66,6 @@ abstract class FirProvidedDeclarationsForMetadataService : FirSessionComponent {
     abstract fun getProvidedTopLevelDeclarations(packageFqName: FqName, scopeSession: ScopeSession): List<FirDeclaration>
     abstract fun getProvidedConstructors(owner: FirClassSymbol<*>, scopeSession: ScopeSession): List<FirConstructor>
     abstract fun getProvidedCallables(owner: FirClassSymbol<*>, scopeSession: ScopeSession): List<FirCallableDeclaration>
-    abstract fun getProvidedNestedClassifiers(owner: FirClassSymbol<*>, scopeSession: ScopeSession): List<FirClassLikeSymbol<*>>
 
     abstract fun registerDeclaration(declaration: FirCallableDeclaration)
 
@@ -105,11 +104,6 @@ private class FirProvidedDeclarationsForMetadataServiceImpl(private val session:
         return memberCache[owner]?.providedCallables ?: emptyList()
     }
 
-    override fun getProvidedNestedClassifiers(owner: FirClassSymbol<*>, scopeSession: ScopeSession): List<FirClassLikeSymbol<*>> {
-        // TODO: remove
-        return emptyList()
-    }
-
     private class ClassDeclarations {
         val providedCallables: MutableList<FirCallableDeclaration> = mutableListOf()
         val providedConstructors: MutableList<FirConstructor> = mutableListOf()