FIR2IR: add extension receiver parameters to functions

compiler/testData/ir/irText/expressions/objectReference.fir.txt

@@ -146,7 +146,8 @@ FILE fqName:<root> fileName:/objectReference.kt
       overridden:
         public open fun toString (): kotlin.String declared in kotlin.Any
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any 
-  FUN name:test visibility:public modality:FINAL <> () returnType:kotlin.Unit 
+  FUN name:test visibility:public modality:FINAL <> ($receiver:<root>.Z) returnType:kotlin.Unit
+    $receiver: VALUE_PARAMETER name:<this> type:<root>.Z
     BLOCK_BODY
       SET_FIELD 'FIELD PROPERTY_BACKING_FIELD name:counter type:kotlin.Int visibility:public ' type=kotlin.Int origin=null
         value: CONST Int type=kotlin.Int value=1