Add missing Python dependencies for ORT training (#7104)

* Add missing Python dependencies for training

cerberus - option parsing
h5py - checkpoint
onnx - model proto
packaging/sympy - symbolic shape inference

* Separate requirements.txt for inference and training Python packages.

requirements-training.txt

@@ -0,0 +1,8 @@
+cerberus
+flatbuffers
+h5py
+numpy >= 1.16.6
+onnx
+packaging
+protobuf
+sympy

setup.py

@@ -232,11 +232,14 @@ def run(self):
     'onnxruntime.transformers.longformer',
 ]
 
+requirements_file = "requirements.txt"
+
 if '--enable_training' in sys.argv:
     packages.extend(['onnxruntime.training',
                      'onnxruntime.training.amp',
                      'onnxruntime.training.optim'])
     sys.argv.remove('--enable_training')
+    requirements_file = "requirements-training.txt"
 
 package_data = {}
 data_files = []
@@ -310,12 +313,12 @@ def run(self):
     cmd_classes['bdist_wheel'] = bdist_wheel
 cmd_classes['build_ext'] = build_ext
 
-requirements_path = path.join(getcwd(), "requirements.txt")
+requirements_path = path.join(getcwd(), requirements_file)
 if not path.exists(requirements_path):
     this = path.dirname(__file__)
-    requirements_path = path.join(this, "requirements.txt")
+    requirements_path = path.join(this, requirements_file)
 if not path.exists(requirements_path):
-    raise FileNotFoundError("Unable to find 'requirements.txt'")
+    raise FileNotFoundError("Unable to find " + requirements_file)
 with open(requirements_path) as f:
     install_requires = f.read().splitlines()