Default to opset 21 in extra_options for ONNX models (#421)

Adds overrides for `update_extra_options()` to `AzureDownloadableModel`
and `OnnxModelZooDownloadableModel` to set opset version to 21 during
import.

Fixes CI failures introduced by the removal of the `--opset-version`
flag in commit `9215c13b696aa8ca767207c15e63a2dff6eccccf`.

alt_e2eshark/onnx_tests/helper_classes.py

@@ -14,7 +14,7 @@
 from onnx.helper import make_node, make_graph, make_model
 from pathlib import Path
 from e2e_testing import azutils
-from e2e_testing.framework import OnnxModelInfo, TestTensors
+from e2e_testing.framework import ExtraOptions, ImporterOptions, OnnxModelInfo, TestTensors
 from e2e_testing.onnx_utils import (
     modify_model_output,
     find_node,
@@ -113,6 +113,10 @@ def __init__(self, is_validated: bool, model_url: str, name: str, onnx_model_pat
             os.mkdir(self.cache_dir)
         super().__init__(name, onnx_model_path, opset_version)
 
+    def update_extra_options(self):
+        # Default to using opset version 21 for all ONNX Model Zoo models.
+        self.extra_options = ExtraOptions(import_model_options=ImporterOptions(opset_version=21))
+
     def unzip_model_archive(self, tar_path):
         model_dir = str(Path(self.model).parent)
         with tarfile.open(tar_path) as tar:
@@ -229,6 +233,10 @@ def __init__(self, name: str, onnx_model_path: str):
         self.cache_dir = os.path.join(parent_cache_dir, name)
         super().__init__(name, onnx_model_path, opset_version)
 
+    def update_extra_options(self):
+        # Default to using opset version 21 for all Azure models.
+        self.extra_options = ExtraOptions(import_model_options=ImporterOptions(opset_version=21))
+
     def update_sess_options(self):
         self.sess_options.graph_optimization_level = onnxruntime.GraphOptimizationLevel.ORT_DISABLE_ALL