Track fake overrides for IrField

compiler/testData/ir/irText/expressions/multipleThisReferences.txt

@@ -98,6 +98,9 @@ FILE fqName:<root> fileName:/multipleThisReferences.kt
                       GET_FIELD 'xx: Int' type=kotlin.Int origin=null
                         receiver: GET_VAR 'this@<no name provided>: <no name provided>' type=Host.test.<no name provided> origin=null
               PROPERTY FAKE_OVERRIDE name:x visibility:public modality:FINAL flags:val
+                FIELD FAKE_OVERRIDE name:x type:kotlin.Int visibility:public flags:final
+                  overridden:
+                    FIELD PROPERTY_BACKING_FIELD name:x type:kotlin.Int visibility:public flags:final
                 FUN FAKE_OVERRIDE name:<get-x> visibility:public modality:FINAL <> ($this:Outer.Inner) returnType:kotlin.Int flags:
                   correspondingProperty: PROPERTY FAKE_OVERRIDE name:x visibility:public modality:FINAL flags:val
                   overridden:
@@ -130,4 +133,3 @@ FILE fqName:<root> fileName:/multipleThisReferences.kt
       overridden:
         FUN IR_EXTERNAL_DECLARATION_STUB name:toString visibility:public modality:OPEN <> ($this:kotlin.Any) returnType:kotlin.String flags:
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any flags:
-