Mark Rossetti

[Core] Address MAX_PATH issues on Windows in runtime_env/packaging

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## Description This PR addresses MAX_PATH issues (file lengths longer than 260 character) on Windows in `runtime_env/packaging.py` Prior to these changes, running `test_runtime_env_working_dir` test could fail with errors like >...

The Windows Azure images should use k-sigs/windows-testing infra for image validation

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## Is your feature request related to a problem? Please describe. Recently some Azure Windows images broke sig-windows test passes. Ex: https://github.com/kubernetes/test-infra/pull/34771 where we had to pin the test passes...