cuda namespace collides with libcu++

[jdwapman]

Describe the bug
PR gunrock/essentials#134 fixed some issues with Nvidia's cuda namespace colliding with gunrock's cuda namespace. However, changes in CUDA 11.7 add more conflicts. This does not seem sustainable and I therefore propose renaming gunrock's cuda namespace to something more unique. This may also apply to libraries such as libcu++.

To Reproduce
Use a cooperative groups function such as cg::reduce within an Essentials kernel.

Expected behavior
Code compiles with no issues

Screenshots
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Environment (please complete the following information):

• Linux/Windows (e.g. run lsb_release -a for Linux): Ubuntu 22.04 LTS
• NVIDIA Driver, CUDA version: Driver 515.43.04, CUDA 11.7
• GCC/G++ version: 11.2.0

Additional context
Add any other context about the problem here.