IrFunctionExpression: add 'origin'

This is actually either a LAMBDA or an ANONYMOUS_FUNCTION.
Not quite sure if it's really required, but some tools such as IR-based
decompiler might require this information.

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

@@ -35,7 +35,7 @@ FILE fqName:<root> fileName:/objectReferenceInClosureInSuperConstructorCall.kt
     CONSTRUCTOR visibility:private <> () returnType:<root>.Test [primary] 
       BLOCK_BODY
         DELEGATING_CONSTRUCTOR_CALL 'public constructor <init> (lambda: kotlin.Function0<kotlin.Any>) [primary] declared in <root>.Base'
-          lambda: FUN_EXPR type=IrErrorType
+          lambda: FUN_EXPR type=IrErrorType origin=LAMBDA
             FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:IrErrorType 
               BLOCK_BODY
                 ERROR_CALL 'Unresolved reference: Test#' type=IrErrorType