Common-src develop branch missing required CMake files for UPF build

Building oai-cn5g-upf fails with include could not find requested file: /openair-upf/src/common-src/model/nrf/nrf_model.cmake. The UPF repository expects these CMake modules to be present in the cn5g-common-src submodule, but the current develop head of cn5g-common-src no longer contains them. This breaks the default submodule sync and prevents the UPF from building without manually rolling back or patching the common repository.

To Reproduce

1. Fetch the latest develop branch of oai-cn5g-upf and initialize submodules (which pulls cn5g-common-src@develop).
2. Run the standard Docker build (e.g. docker build --target oai-upf --tag oai-upf:test --file Dockerfile.upf.ubuntu .).
3. Observe CMake configure errors: /openair-upf/src/common-src/model/nrf/nrf_model.cmake (and common_model.cmake) cannot be found.

Expected behavior UPF build completes, with the submodule providing all CMake includes expected by oai-cn5g-upf.

Additional context The build log also shows a long list of cp: cannot create symbolic link … File exists warnings during environment setup, but the fatal failure is the missing CMake files.