[v1.x] Add coverage to onnx test pipeline. (#19682)

* Add coverage to onnx test pipeline.

* Install coveragepy for onnx test suite.

* Export coverage report to xml format so codecov picks it up.

* Revert "Install coveragepy for onnx test suite."

This reverts commit a09cb33.

Co-authored-by: Joe Evans <joeev@amazon.com>

Author: josephevans

ci/docker/runtime_functions.sh

@@ -1273,16 +1273,17 @@ unittest_centos7_gpu() {
 }
 
 integrationtest_ubuntu_cpu_onnx() {
-	set -ex
-	export PYTHONPATH=./python/
-	export MXNET_SUBGRAPH_VERBOSE=0
-	export DMLC_LOG_STACK_TRACE_DEPTH=10
-	tests/python-pytest/onnx/backend_test.py
-	pytest tests/python-pytest/onnx/mxnet_export_test.py
-	pytest tests/python-pytest/onnx/test_models.py
-	pytest tests/python-pytest/onnx/test_node.py
-	pytest tests/python-pytest/onnx/test_operators.py
-	pytest tests/python-pytest/onnx/test_onnxruntime.py
+    set -ex
+    export PYTHONPATH=./python/
+    export MXNET_SUBGRAPH_VERBOSE=0
+    export DMLC_LOG_STACK_TRACE_DEPTH=10
+    tests/python-pytest/onnx/backend_test.py
+    COV_ARG="--cov=./ --cov-report=xml --cov-append"
+    pytest $COV_ARG --verbose tests/python-pytest/onnx/mxnet_export_test.py
+    pytest $COV_ARG --verbose tests/python-pytest/onnx/test_models.py
+    pytest $COV_ARG --verbose tests/python-pytest/onnx/test_node.py
+    pytest $COV_ARG --verbose tests/python-pytest/onnx/test_operators.py
+    pytest $COV_ARG --verbose tests/python-pytest/onnx/test_onnxruntime.py
 }
 
 integrationtest_ubuntu_gpu_python() {