MAINT: remove deprecated distutils usage

The standard distutils package is due to be removed in a future version of Python and the deprecation warning are bugging me. This MR removes all the use of distutils with the recommended alternatives (see here).

bilby/core/sampler/base_sampler.py

@@ -990,8 +990,8 @@ class _TemporaryFileSamplerMixin:
 
             if os.path.exists(self.outputfiles_basename):
                 shutil.copytree(
+                    self.outputfiles_basename,
                     self.temporary_outputfiles_basename,
-                    outputfiles_basename_stripped,
                     dirs_exist_ok=True,
                 )
             check_directory_exists_and_if_not_mkdir(temporary_outputfiles_basename)