docs: Refactor the NVIDIA GPU page

[kimwnasptd]

This PR refactors the Enable NVIDIA GPUs page to

1. Add more commands for verifying the operator is ready
2. Add info sections to explain to users potential issues with the commands
3. Add content on how users can launch a notebook with CUDA and verify the GPU is accessible

cc @afgambin

[kimwnasptd]

@afgambin did one more pass. My last question at this point is, should we rename the how-to guide from Enable NVIDIA GPUs to something else, since the how-to also explains how to create a notebook?

Or another plan could be to keep the title, but move the Launch GPU-enabled notebook under the new section that includes all the how-tos for notebooks.

[afgambin]

@afgambin did one more pass. My last question at this point is, should we rename the how-to guide from Enable NVIDIA GPUs to something else, since the how-to also explains how to create a notebook?

Or another plan could be to keep the title, but move the Launch GPU-enabled notebook under the new section that includes all the how-tos for notebooks.

Let's keep the title, it seems accurate to me, and we'll move the section to the how-to for managing notebooks (once we merge my PR). Filing the Jira ticket.

[kimwnasptd]

Thanks for the review @afgambin!