NoisyExpectedHypervolumeMixin (facebook#1909)

Summary:
X-link: pytorch/botorch#2045

Pull Request resolved: facebook#1909

This commit introduces `NoisyExpectedHypervolumeMixin`, a derivative of `CachedCholeskyMCSamplerMixin` that separates out much of the Pareto-partitioning required for `qNEHVI`.

Differential Revision: D50337502

fbshipit-source-id: dfa9b71d98be22253d004d3c0bad94bb48f5dfb5

ax/models/tests/test_botorch_moo_model.py

@@ -10,6 +10,7 @@
 from unittest import mock
 
 import ax.models.torch.botorch_moo_defaults as botorch_moo_defaults
+import botorch.utils.multi_objective.hypervolume as hypervolume
 import numpy as np
 import torch
 from ax.core.search_space import SearchSpaceDigest
@@ -423,7 +424,7 @@ def test_BotorchMOOModel_with_qehvi(
             _mock_partitioning = es.enter_context(
                 mock.patch(
                     partitioning_path,
-                    wraps=moo_monte_carlo.FastNondominatedPartitioning,
+                    wraps=hypervolume.FastNondominatedPartitioning,
                 )
             )
             torch_opt_config = TorchOptConfig(