FindCUDA: Fix CMP0007 warning in run_nvcc.cmake

This commit sets the CMP0007 policy to NEW for the entire script. Fixes the warning from showing up during the building phase in certain scenarios.

This may be a heavy-handed approach to fixing the problem so let me know if you want me to be more precise with my changes.

Fixes: #16579 (closed)
Topic-rename: FindCUDA-run_nvcc-CMP0007