Generate references to overridden declarations as a separate pass

NB currently it relies on overriddenDescriptors in a FunctionDescriptor,
thus maybe incorrect for transformed declarations.

compiler/testData/ir/irText/lambdas/destructuringInLambda.txt

@@ -55,6 +55,8 @@ FILE fqName:<root> fileName:/destructuringInLambda.kt
             x: GET_VAR 'value-parameter x: Int = ...' type=kotlin.Int origin=null
             y: GET_VAR 'value-parameter y: Int = ...' type=kotlin.Int origin=null
     FUN GENERATED_DATA_CLASS_MEMBER name:toString visibility:public modality:OPEN <> ($this:A) returnType:String flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:toString visibility:public modality:OPEN <> () returnType:String flags:
       $this: VALUE_PARAMETER name:<this> type:A flags:
       BLOCK_BODY
         RETURN type=kotlin.Nothing from='toString(): String'
@@ -69,6 +71,8 @@ FILE fqName:<root> fileName:/destructuringInLambda.kt
               $this: GET_VAR 'this@A: A' type=A origin=null
             CONST String type=kotlin.String value=)
     FUN GENERATED_DATA_CLASS_MEMBER name:hashCode visibility:public modality:OPEN <> ($this:A) returnType:Int flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:hashCode visibility:public modality:OPEN <> () returnType:Int flags:
       $this: VALUE_PARAMETER name:<this> type:A flags:
       BLOCK_BODY
         VAR IR_TEMPORARY_VARIABLE name:tmp0_result type:kotlin.Int flags:var
@@ -88,6 +92,8 @@ FILE fqName:<root> fileName:/destructuringInLambda.kt
         RETURN type=kotlin.Nothing from='hashCode(): Int'
           GET_VAR 'tmp0_result: Int' type=kotlin.Int origin=null
     FUN GENERATED_DATA_CLASS_MEMBER name:equals visibility:public modality:OPEN <> ($this:A, other:kotlin.Any?) returnType:Boolean flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:equals visibility:public modality:OPEN <> (other:kotlin.Any?) returnType:Boolean flags:
       $this: VALUE_PARAMETER name:<this> type:A flags:
       VALUE_PARAMETER name:other index:0 type:kotlin.Any? flags:
       BLOCK_BODY

compiler/testData/ir/irText/lambdas/multipleImplicitReceivers.txt

@@ -6,11 +6,17 @@ FILE fqName:<root> fileName:/multipleImplicitReceivers.kt
         DELEGATING_CONSTRUCTOR_CALL 'constructor Any()'
         INSTANCE_INITIALIZER_CALL classDescriptor='A'
     FUN FAKE_OVERRIDE name:equals visibility:public modality:OPEN <> ($this:kotlin.Any, other:kotlin.Any?) returnType:Boolean flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:equals visibility:public modality:OPEN <> (other:kotlin.Any?) returnType:Boolean flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
       VALUE_PARAMETER name:other index:0 type:kotlin.Any? flags:
     FUN FAKE_OVERRIDE name:hashCode visibility:public modality:OPEN <> ($this:kotlin.Any) returnType:Int flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:hashCode visibility:public modality:OPEN <> () returnType:Int flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
     FUN FAKE_OVERRIDE name:toString visibility:public modality:OPEN <> ($this:kotlin.Any) returnType:String flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:toString visibility:public modality:OPEN <> () returnType:String flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
   CLASS OBJECT name:B modality:FINAL visibility:public flags:
     $this: VALUE_PARAMETER INSTANCE_RECEIVER name:<this> type:B flags:
@@ -19,11 +25,17 @@ FILE fqName:<root> fileName:/multipleImplicitReceivers.kt
         DELEGATING_CONSTRUCTOR_CALL 'constructor Any()'
         INSTANCE_INITIALIZER_CALL classDescriptor='B'
     FUN FAKE_OVERRIDE name:equals visibility:public modality:OPEN <> ($this:kotlin.Any, other:kotlin.Any?) returnType:Boolean flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:equals visibility:public modality:OPEN <> (other:kotlin.Any?) returnType:Boolean flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
       VALUE_PARAMETER name:other index:0 type:kotlin.Any? flags:
     FUN FAKE_OVERRIDE name:hashCode visibility:public modality:OPEN <> ($this:kotlin.Any) returnType:Int flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:hashCode visibility:public modality:OPEN <> () returnType:Int flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
     FUN FAKE_OVERRIDE name:toString visibility:public modality:OPEN <> ($this:kotlin.Any) returnType:String flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:toString visibility:public modality:OPEN <> () returnType:String flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
   CLASS INTERFACE name:IFoo modality:ABSTRACT visibility:public flags:
     $this: VALUE_PARAMETER INSTANCE_RECEIVER name:<this> type:IFoo flags:
@@ -35,11 +47,17 @@ FILE fqName:<root> fileName:/multipleImplicitReceivers.kt
           RETURN type=kotlin.Nothing from='<get-foo>() on A: B'
             GET_OBJECT 'B' type=B
     FUN FAKE_OVERRIDE name:equals visibility:public modality:OPEN <> ($this:kotlin.Any, other:kotlin.Any?) returnType:Boolean flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:equals visibility:public modality:OPEN <> (other:kotlin.Any?) returnType:Boolean flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
       VALUE_PARAMETER name:other index:0 type:kotlin.Any? flags:
     FUN FAKE_OVERRIDE name:hashCode visibility:public modality:OPEN <> ($this:kotlin.Any) returnType:Int flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:hashCode visibility:public modality:OPEN <> () returnType:Int flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
     FUN FAKE_OVERRIDE name:toString visibility:public modality:OPEN <> ($this:kotlin.Any) returnType:String flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:toString visibility:public modality:OPEN <> () returnType:String flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
   CLASS INTERFACE name:IInvoke modality:ABSTRACT visibility:public flags:
     $this: VALUE_PARAMETER INSTANCE_RECEIVER name:<this> type:IInvoke flags:
@@ -50,11 +68,17 @@ FILE fqName:<root> fileName:/multipleImplicitReceivers.kt
         RETURN type=kotlin.Nothing from='invoke() on B: Int'
           CONST Int type=kotlin.Int value=42
     FUN FAKE_OVERRIDE name:equals visibility:public modality:OPEN <> ($this:kotlin.Any, other:kotlin.Any?) returnType:Boolean flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:equals visibility:public modality:OPEN <> (other:kotlin.Any?) returnType:Boolean flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
       VALUE_PARAMETER name:other index:0 type:kotlin.Any? flags:
     FUN FAKE_OVERRIDE name:hashCode visibility:public modality:OPEN <> ($this:kotlin.Any) returnType:Int flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:hashCode visibility:public modality:OPEN <> () returnType:Int flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
     FUN FAKE_OVERRIDE name:toString visibility:public modality:OPEN <> ($this:kotlin.Any) returnType:String flags:
+      overridden:
+        FUN IR_EXTERNAL_DECLARATION_STUB name:toString visibility:public modality:OPEN <> () returnType:String flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
   FUN name:test visibility:public modality:FINAL <> (fooImpl:IFoo, invokeImpl:IInvoke) returnType:Unit flags:
     VALUE_PARAMETER name:fooImpl index:0 type:IFoo flags: