Bring back ax/benchmark/__init__.py (#2719)

Summary:
Removing `__init__.py` makes the module not discoverable when installed with `pip`, leading to `ModuleNotFoundError: No module named 'ax.benchmark'`. See https://github.com/pytorch/botorch/actions/runs/10581831529/job/29320089546

Pull Request resolved: #2719

Reviewed By: mpolson64

Differential Revision: D61861709

Pulled By: saitcakmak

fbshipit-source-id: 612cf84dc3e0a13293bf61f0b3151369919c838c

ax/benchmark/__init__.py

@@ -0,0 +1,5 @@
+#!/usr/bin/env python3
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.

sphinx/source/benchmark.rst

@@ -10,7 +10,6 @@ ax.benchmark
 Benchmark
 ---------
 
-
 Benchmark Method
 ~~~~~~~~~~~~~~~~
 
@@ -19,6 +18,14 @@ Benchmark Method
     :undoc-members:
     :show-inheritance:
 
+Benchmark Metric
+~~~~~~~~~~~~~~~~
+
+.. automodule:: ax.benchmark.benchmark_metric
+    :members:
+    :undoc-members:
+    :show-inheritance:
+
 Benchmark Problem
 ~~~~~~~~~~~~~~~~~~
 
@@ -60,38 +67,6 @@ Benchmark Methods Sobol
     :undoc-members:
     :show-inheritance:
 
-Benchmark Metrics Base
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. automodule:: ax.benchmark.metrics.base
-    :members:
-    :undoc-members:
-    :show-inheritance:
-
-Benchmark Metrics Benchmark
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. automodule:: ax.benchmark.metrics.benchmark
-    :members:
-    :undoc-members:
-    :show-inheritance:
-
-Benchmark Metrics Jenatton
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. automodule:: ax.benchmark.metrics.jenatton
-    :members:
-    :undoc-members:
-    :show-inheritance:
-
-Benchmark Metrics Utils
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. automodule:: ax.benchmark.metrics.utils
-    :members:
-    :undoc-members:
-    :show-inheritance:
-
 Benchmark Problems Registry
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~