[FE] Extract computation of sealed class inheritors into separate component

This is needed to provide more optimal provider in IDE plugin

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/context.kt

@@ -27,6 +27,7 @@ import org.jetbrains.kotlin.metadata.ProtoBuf
 import org.jetbrains.kotlin.metadata.deserialization.*
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.protobuf.ExtensionRegistryLite
+import org.jetbrains.kotlin.resolve.SealedClassInheritorsProvider
 import org.jetbrains.kotlin.resolve.constants.ConstantValue
 import org.jetbrains.kotlin.resolve.sam.SamConversionResolver
 import org.jetbrains.kotlin.serialization.deserialization.descriptors.DeserializedContainerSource

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/descriptors/DeserializedClassDescriptor.kt

@@ -18,8 +18,8 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.DescriptorFactory
 import org.jetbrains.kotlin.resolve.NonReportingOverrideStrategy
 import org.jetbrains.kotlin.resolve.OverridingUtil
+import org.jetbrains.kotlin.resolve.SealedClassInheritorsProviderImpl
 import org.jetbrains.kotlin.resolve.descriptorUtil.classId
-import org.jetbrains.kotlin.resolve.descriptorUtil.computeSealedSubclasses
 import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter
 import org.jetbrains.kotlin.resolve.scopes.MemberScope
 import org.jetbrains.kotlin.resolve.scopes.StaticScopeForKotlinEnum
@@ -165,7 +165,7 @@ class DeserializedClassDescriptor(
         }
 
         // This is needed because classes compiled with Kotlin 1.0 did not contain the sealed_subclass_fq_name field
-        return computeSealedSubclasses(this, freedomForSealedInterfacesSupported = false)
+        return SealedClassInheritorsProviderImpl.computeSealedSubclasses(this, freedomForSealedInterfacesSupported = false)
     }
 
     override fun getSealedSubclasses() = sealedSubclasses()