Read a delivery receipt's body as the octets that arrived (#81)

* Regression tests for a receipt body read under a data_coding it is not written in

* Read a delivery receipt's body as the octets that arrived, not by its data_coding

* Assert SMPPSim's UCS2 receipt body parses like every other segment's

* Record the receipt-body defect as fixed

* Retain a multipart segment's octets once, not twice

* Sort the new type import into its file's order

src/pdu-framer.ts

@@ -1,5 +1,5 @@
 import type { Result } from './result.ts';
-import { framingRefusal } from './pdu.ts';
+import { framingRefusal } from './pdu-refusal.ts';
 
 /**
  * Cuts a byte stream into whole PDUs.