[C++] CMake cannot find CUDA toolkit

For some reason, after a conda update it seems that CMake is not able to find the CUDA toolkit anymore:
```Java

-- Unable to find cudart library.
CMake Error at /home/antoine/miniconda3/envs/pyarrow/share/cmake-3.23/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
Could NOT find CUDAToolkit (missing: CUDA_CUDART) (found version
"10.1.243")
Call Stack (most recent call first):
/home/antoine/miniconda3/envs/pyarrow/share/cmake-3.23/Modules/FindPackageHandleStandardArgs.cmake:594 (_FPHSA_FAILURE_MESSAGE)
/home/antoine/miniconda3/envs/pyarrow/share/cmake-3.23/Modules/FindCUDAToolkit.cmake:818 (find_package_handle_standard_args)
src/arrow/gpu/CMakeLists.txt:40 (find_package)

-- Configuring incomplete, errors occurred!
```

which is weird as the CUDA toolkit is installed as a Ubuntu package.

**Reporter**: [Antoine Pitrou](https://issues.apache.org/jira/browse/ARROW-16462) / @pitrou
#### Related issues:
- [[C++] Cannot build with system CUDA toolkit and conda-forge compilers](https://github.com/apache/arrow/issues/31333) (supercedes)

_{**Note**: *This issue was originally created as [ARROW-16462](https://issues.apache.org/jira/browse/ARROW-16462). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Read related issue #31333 first, since it supersedes this report. Then inspect src/arrow/gpu/CMakeLists.txt around line 40 and reproduce the CMake configuration failure; done means the reported setup can find the CUDA toolkit during configuration.

Written by the indexing model from the issue text.