consistently serialize strings to MemorySegment instead of addresses

(Longs) and remove ad-hoc upcall-class Long to MemorySegment conversion

src/clj/coffi/ffi.clj

@@ -499,10 +499,6 @@
                                     inc)))
                          acc))
                      [:invokeinterface IFn "invoke" (repeat (inc (count arg-types)) Object)]
-                     (if (identical? ::mem/pointer (mem/primitive-type ret-type))
-                       [[:checkcast Long]
-                        [:invokevirtual Long "longValue" [:long]]
-                        [:invokestatic MemorySegment "ofAddress" [:long MemorySegment] true]])
                      (to-prim-asm ret-type)
                      [(return-for-type ret-type :areturn)]]}]})
 

src/clj/coffi/mem.clj

@@ -1247,7 +1247,7 @@
 (defmethod serialize* ::c-string
   [obj _type ^Arena session]
   (if obj
-    (address-of (.allocateFrom session ^String obj))
+    (.allocateFrom session ^String obj)
     (MemorySegment/NULL)))
 
 (defmethod deserialize* ::c-string