Replace deprecated find_module with find_spec (importlib)

find_module was deprecated with python 3.4 and python 3.12
removed it (https://docs.python.org/3.12/whatsnew/3.12.html#importlib).

The new command is find_spec and only required a few adaptions

capnp/lib/capnp.pyx

@@ -42,6 +42,7 @@ from types import ModuleType as _ModuleType
 from operator import attrgetter as _attrgetter
 from functools import partial as _partial
 from contextlib import asynccontextmanager as _asynccontextmanager
+from importlib.machinery import ModuleSpec
 
 _CAPNP_VERSION_MAJOR = capnp.CAPNP_VERSION_MAJOR
 _CAPNP_VERSION_MINOR = capnp.CAPNP_VERSION_MINOR
@@ -4322,7 +4323,7 @@ class _Importer:
         self.extension = '.capnp'
         self.additional_paths = additional_paths
 
-    def find_module(self, fullname, package_path=None):
+    def find_spec(self, fullname, package_path, target=None):
         if fullname in _sys.modules: # Don't allow re-imports
             return None
 
@@ -4363,12 +4364,12 @@ class _Importer:
                 path = abspath(path)
 
             if is_file(path+sep+capnp_module_name):
-                return _Loader(fullname, join_path(path, capnp_module_name), self.additional_paths)
+                return ModuleSpec(fullname, _Loader(fullname, join_path(path, capnp_module_name), self.additional_paths))
             if has_underscores:
                 if is_file(path+sep+capnp_module_name_dashes):
-                    return _Loader(fullname, join_path(path, capnp_module_name_dashes), self.additional_paths)
+                    return ModuleSpec(fullname, _Loader(fullname, join_path(path, capnp_module_name_dashes), self.additional_paths))
                 if is_file(path+sep+capnp_module_name_spaces):
-                    return _Loader(fullname, join_path(path, capnp_module_name_spaces), self.additional_paths)
+                    return ModuleSpec(fullname, _Loader(fullname, join_path(path, capnp_module_name_spaces), self.additional_paths))
 
 
 _importer = None