[IR] Introduce new functions for referencing declarations from IrPluginContext

Those functions take `ClassId` and `CallableId`, which is more correct
  than using just `FqName`.

Also implement those functions for `Fir2IrPluginContext`

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/extensions/IrPluginContext.kt

@@ -16,6 +16,8 @@ import org.jetbrains.kotlin.ir.util.IdSignature
 import org.jetbrains.kotlin.ir.util.IrMessageLogger
 import org.jetbrains.kotlin.ir.util.ReferenceSymbolTable
 import org.jetbrains.kotlin.ir.util.TypeTranslator
+import org.jetbrains.kotlin.name.CallableId
+import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.platform.TargetPlatform
 import org.jetbrains.kotlin.resolve.BindingContext
@@ -53,6 +55,13 @@ interface IrPluginContext : IrGeneratorContext {
     fun referenceFunctions(fqName: FqName): Collection<IrSimpleFunctionSymbol>
     fun referenceProperties(fqName: FqName): Collection<IrPropertySymbol>
 
+    // This one is experimental too
+    fun referenceClass(classId: ClassId): IrClassSymbol?
+    fun referenceTypeAlias(classId: ClassId): IrTypeAliasSymbol?
+    fun referenceConstructors(classId: ClassId): Collection<IrConstructorSymbol>
+    fun referenceFunctions(callableId: CallableId): Collection<IrSimpleFunctionSymbol>
+    fun referenceProperties(callableId: CallableId): Collection<IrPropertySymbol>
+
     // temporary solution to load synthetic top-level declaration
     fun referenceTopLevel(signature: IdSignature, kind: IrDeserializer.TopLevelSymbolKind, moduleDescriptor: ModuleDescriptor): IrSymbol?
 }

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/extensions/IrPluginContextImpl.kt

@@ -20,6 +20,8 @@ import org.jetbrains.kotlin.ir.util.IdSignature
 import org.jetbrains.kotlin.ir.util.IrMessageLogger
 import org.jetbrains.kotlin.ir.util.ReferenceSymbolTable
 import org.jetbrains.kotlin.ir.util.TypeTranslator
+import org.jetbrains.kotlin.name.CallableId
+import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.platform.TargetPlatform
 import org.jetbrains.kotlin.resolve.BindingContext
@@ -140,6 +142,26 @@ open class IrPluginContextImpl constructor(
         }
     }
 
+    override fun referenceClass(classId: ClassId): IrClassSymbol? {
+        return referenceClass(classId.asSingleFqName())
+    }
+
+    override fun referenceTypeAlias(classId: ClassId): IrTypeAliasSymbol? {
+        return referenceTypeAlias(classId.asSingleFqName())
+    }
+
+    override fun referenceConstructors(classId: ClassId): Collection<IrConstructorSymbol> {
+        return referenceConstructors(classId.asSingleFqName())
+    }
+
+    override fun referenceFunctions(callableId: CallableId): Collection<IrSimpleFunctionSymbol> {
+        return referenceFunctions(callableId.asSingleFqName())
+    }
+
+    override fun referenceProperties(callableId: CallableId): Collection<IrPropertySymbol> {
+        return referenceProperties(callableId.asSingleFqName())
+    }
+
     override fun referenceTopLevel(
         signature: IdSignature,
         kind: IrDeserializer.TopLevelSymbolKind,