Unskip integ tests mlops

[lucasjia-aws]

Summary

5 integ tests in sagemaker-mlops were conditionally skipped via @pytest.mark.skipif because they require SageMaker Spark container images, which only support Python 3.9 and 3.12. Since CI runs integ tests on Python 3.10, these tests were never executed.

This PR introduces a spark_py312 marker to split mlops integ tests into two groups:

• py310: runs all integ tests excluding spark_py312
• py312: runs only spark_py312 marked tests (Spark/Feature Processor tests that depend on SageMaker Spark images)

This allows both groups to run in CI without version conflicts. The corresponding buildspec change to add the py312 step will be done separately in the CI infra (SageMakerMLFPySDKInfraCDK).

Changes

• Register spark_py312 marker in sagemaker-mlops/tox.ini
• Replace @pytest.mark.skipif with @pytest.mark.spark_py312 on 4 tests in test_feature_processor_integ.py
• Add @pytest.mark.spark_py312 to 1 test in test_feature_processor_spark_compat.py
• test_to_pipeline_and_execute_with_lake_formation remains skipped (@pytest.mark.skip) due to unresolved Lake Formation environment configuration in CI (tracked separately)

Testing

Validated via CodeBuild in Prod:

• py310 with -m "not spark_py312": all tests pass, spark tests correctly excluded
• py312 with -m spark_py312: 4/5 tests pass, 1 skipped (Lake Formation)