Update of NVHPC easyblock for #3527

This is one of the best examples of the advantages of ModuleLoadEnvironment:

• it removed the need for a helper method like _nvhpc_extended_components()
• any path can be easily removed from $VARIABLE instead of deleting the variable (e.g. with BYO)
• it is more clear when a $VARIABLE gets paths appended or if it is re-assigned

Tested with a default easyconfig and also enabling the following easyconfig parameters:

module_byo_compilers = True  # Remove compilers from PATH (Bring-your-own compilers)
module_nvhpc_own_mpi = True  # Add NVHPC's own pre-compiled OpenMPI
module_add_math_libs = True  # Add NVHPC's math libraries (which should be there from CUDA anyway)
module_add_profilers = True  # Add NVHPC's NVIDIA Profilers
module_add_nccl = True       # Add NVHPC's NCCL library
module_add_nvshmem = True    # Add NVHPC's NVSHMEM library
module_add_cuda = True       # Add NVHPC's bundled CUDA

Bonus:

• fix sanity checks with module_byo_compilers enabled
• add CMAKE_MODULE_PATH to module environment