test all the different loss functions in each test

Improve the tests

• test all the different loss functions in each test
• add Learner1D._recompute_losses_factor to remove xfail from two tests
• speed up the tests

adaptive/learner/data_saver.py

@@ -35,6 +35,9 @@ class DataSaver:
     def __getattr__(self, attr):
         return getattr(self.learner, attr)
 
+    def __setattr__(self, attr):
+        return setattr(self.learner, attr)
+
     @copy_docstring_from(BaseLearner.tell)
     def tell(self, x, result):
         y = self.arg_picker(result)