UCC PG build in CI (#81583)
- Modifies the current cmake build definitions to use `find_package` to find UCX and UCC installed in the system
- Install UCX and UCC in CUDA dockers
- Build PyTorch with `USE_UCC=1` in pipelines
- Currently, we are not running unit tests with the UCC PG. Those tests will be added in future PRs.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/81583
Approved by: https://github.com/vtlam, https://github.com/malfet
