Refactor AnnotationImplementationLowering

- Replaced UNDEFINED_OFFSET with SYNTHETIC_OFFSET, it's required by
  Native backend codegen
- Fixed missing overridden symbols
- Enforce adding fakeoverrides for members not overridden by backend
- Support more points for platform customisation

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/DataClassMembersGenerator.kt

@@ -7,7 +7,6 @@ package org.jetbrains.kotlin.ir.util
 
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
-import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.impl.IrVariableImpl
@@ -36,7 +35,8 @@ abstract class DataClassMembersGenerator(
     val context: IrGeneratorContext,
     val symbolTable: ReferenceSymbolTable,
     val irClass: IrClass,
-    val origin: IrDeclarationOrigin
+    val origin: IrDeclarationOrigin,
+    val forbidDirectFieldAccess: Boolean = false
 ) {
     private val irPropertiesByDescriptor: Map<PropertyDescriptor, IrProperty> =
         irClass.properties.associateBy { it.descriptor }
@@ -49,8 +49,8 @@ abstract class DataClassMembersGenerator(
         }
 
     private inner class MemberFunctionBuilder(
-        startOffset: Int = UNDEFINED_OFFSET,
-        endOffset: Int = UNDEFINED_OFFSET,
+        startOffset: Int = SYNTHETIC_OFFSET,
+        endOffset: Int = SYNTHETIC_OFFSET,
         val irFunction: IrFunction
     ) : IrBlockBodyBuilder(context, Scope(irFunction.symbol), startOffset, endOffset) {
         inline fun addToClass(builder: MemberFunctionBuilder.(IrFunction) -> Unit): IrFunction {
@@ -89,7 +89,7 @@ abstract class DataClassMembersGenerator(
             // data classes and corresponding properties can be non-final.
             // We should use getters for such properties (see KT-41284).
             val backingField = property.backingField
-            return if (property.modality == Modality.FINAL && backingField != null) {
+            return if (!forbidDirectFieldAccess && property.modality == Modality.FINAL && backingField != null) {
                 irGetField(receiver, backingField)
             } else {
                 irCall(property.getter!!).apply {