Add option to skip certain unit tests (#2878)

Summary:

Add option to skip certain tests - useful when a few tests are broken and we need to skip them to gain visibility in other unit tests. This usually happens on our CPU unit tests, so only modifying this script.


To use, simply add the name of the tests to skip in this txt file. such as:

```
test_sharding_fused_ebc_as_top_level
```

You can also use the class name for the test: e.g. 
```
ModelParallelSparseOnlyTestGloo
```

Differential Revision: D72815908

Author: aporialiao

.github/scripts/tests_to_skip.txt

@@ -0,0 +1,4 @@
+test_dynamic_shape_ebc
+test_correctness
+test_numerical_stability
+test_basic

.github/workflows/unittest_ci_cpu.yml

@@ -72,6 +72,14 @@ jobs:
           python -c "import numpy"
         echo "numpy succeeded"
         conda install -n build_binary -y pytest
+        # Read the list of tests to skip from a file, ignoring empty lines and comments
+        skip_expression=$(awk '!/^($|#)/ {printf " and not %s", $0}' ./.github/scripts/tests_to_skip.txt)
+        # Check if skip_expression is effectively empty
+        if [ -z "$skip_expression" ]; then
+          skip_expression=""
+        else
+          skip_expression=${skip_expression:5}  # Remove the leading " and "
+        fi
         conda run -n build_binary \
           python -m pytest torchrec -v -s -W ignore::pytest.PytestCollectionWarning --continue-on-collection-errors \
-          --ignore-glob=**/test_utils/
+          --ignore-glob=**/test_utils/ -k "$skip_expression"