Created a deep copier good for fake overrides.

Adapted it from inliner copier.
It is capable of producing type substituted members.

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/inline/DeepCopyIrTreeWithDescriptors.kt

@@ -21,7 +21,6 @@ import org.jetbrains.kotlin.ir.visitors.acceptVoid
 import org.jetbrains.kotlin.name.Name
 
 internal class DeepCopyIrTreeWithSymbolsForInliner(
-    val context: CommonBackendContext,
     val typeArguments: Map<IrTypeParameterSymbol, IrType?>?,
     val parent: IrDeclarationParent?
 ) {

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/inline/FunctionInlining.kt

@@ -120,7 +120,7 @@ class FunctionInlining(
                 (0 until callSite.typeArgumentsCount).map {
                     typeParameters[it].symbol to callSite.getTypeArgument(it)
                 }.associate { it }
-            DeepCopyIrTreeWithSymbolsForInliner(context, typeArguments, parent)
+            DeepCopyIrTreeWithSymbolsForInliner(typeArguments, parent)
         }
 
         val substituteMap = mutableMapOf<IrValueParameter, IrExpression>()