refactor(clew): model object dumper as Python library

src/clew/BUILD.bazel

@@ -1,9 +1,16 @@
-load("@rules_python//python:defs.bzl", "py_binary")
+load("@rules_python//python:defs.bzl", "py_binary", "py_library")
+
+py_library(
+    name = "renpy_object_dump",
+    srcs = ["renpy_object_dump.py"],
+)
 
 py_binary(
     name = "clew",
     srcs = ["clew.py"],
-    data = ["renpy_object_dump.py"],
     main = "clew.py",
-    deps = ["//third_party/python:rpycdec"],
+    deps = [
+        ":renpy_object_dump",
+        "//third_party/python:rpycdec",
+    ],
 )