fix: gloo backend

[myungjin]

Description

gloo backend doesn't work with isend/irecv (asynchronous point-to-point ops). See https://github.com/pytorch/pytorch/issues/30723. To mitigate the issue, we use a blocking version (send/recv) for gloo.

Type of Change

• [x] Bug Fix
• [ ] New Feature
• [ ] Breaking Change
• [ ] Refactor
• [ ] Documentation
• [ ] Other (please describe)

Checklist

• [ ] I have read the contributing guidelines
• [ ] Existing issues have been referenced (where applicable)
• [ ] I have verified this change is not present in other open pull requests
• [ ] Functionality is documented
• [ ] All code style checks pass
• [ ] New code contribution is covered by automated tests
• [ ] All new and existing tests pass