Updating the order of conditional checks to load library files in the Cuda component

[Treece-Burgess]

Pull Request Description

This PR updates the ordering of conditional checks in the Cuda component. Specifically for the functions load_cudart_sym,load_cupti_common_sym, and load_nvpw_sym.

Current master has the following workflow of checks:

1. Check to see if PAPI_CUDA_RUNTIME/PAPI_CUDA_CUPTI/PAPI_CUDA_PERFWORKS are set, if so we will search this path for the necessary library files.
2. Use dl_iterate_phdr() to walk through the list of shared objects linked in the executable.
3. Check to see if PAPI_CUDA_ROOT is set and the previous two steps failed; we then search the path that PAPI_CUDA_ROOT is set to for the necessary library files.
4. We use dlopen.

This PR updates the workflow of checks to:

1. Check to see if PAPI_CUDA_RUNTIME/PAPI_CUDA_CUPTI/PAPI_CUDA_PERFWORKS are set, if so we will search this path for the necessary library files.
2. Check to see if PAPI_CUDA_ROOT is set and the previous step failed; we then search the path that PAPI_CUDA_ROOT is set to for the necessary library files.
3. Use dl_iterate_phdr() to walk through the list of shared objects linked in the executable.
4. We use dlopen.

This is being done since we state in the documentation that PAPI_CUDA_ROOT is needed for both runtime and compilation.

Tested on Leconte with eight Tesla V100's with results:

• If PAPI_CUDA_RUNTIME/PAPI_CUDA_CUPTI/PAPI_CUDA_PERFWORKS are set these do indeed take precedent as expected.
• If we do not set the above environment variables and a user has set PAPI_CUDA_ROOT then we do have successfully have this as the second option to be searched.
• If neither of the above mentioned environment variables are set, we do search the linux default directories.

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