Improve nvidia device plugin and dra driver deploy ux

[anson627]

This pull request updates the naming and documentation for NVIDIA GPU deployment options in the AKS deployment CLI and its usage guide. The changes clarify the distinction between the NVIDIA GPU Device Plugin and the NVIDIA DRA Driver, making the CLI flags and documentation more descriptive and consistent.

CLI flag and error message updates:

• Renamed the --gpu-device-plugin flag to --nvidia-device-plugin and the --dra-driver flag to --nvidia-dra-driver in deploy.go to clarify which NVIDIA plugin is being installed.
• Updated error messages in gpu.go to reference the new flag names (--nvidia-device-plugin and --nvidia-dra-driver). [1] [2]

Deployment logic changes:

• Changed the Helm install command in installGPUDevicePlugin to use the namespace nvidia instead of nvidia-device-plugin for consistency with recommended practices.

Documentation improvements:

• Updated karpenter.md to explain the difference between the NVIDIA GPU Device Plugin and the NVIDIA DRA Driver, and to use the new CLI flag names in all example commands and notes. [1] [2]