Enumerate Nvidia GPU IDs

[jailuthra]

What does this pull request do? Explain your changes. (required)

Automatically utilize all available Nvidia GPUs for transcoding, if the user sets the command line parameter as -nvidia=all or -nvidia all.

Specific updates (required)

See commit history

How did you test each of these updates (required)

Manually tested, and verified correct behaviour on:

• Linux desktop with a single GTX 1060 6gb
• Linux intel laptop with no nvidia GPU
• Berlin staging pod with multiple nvidia GPUs
• Eli's test on a windows machine

Does this pull request close any open issues?

Fixes #1205

Checklist:

• Read the contribution guide
• make runs successfully
• All tests in ./test.sh pass
• README and other documentation updated
• Pending changelog updated

[iameli]

Tested on Windows, working great!

[yondonfu]

Since we're using a package that gives us access to all device info now, an additional UX improvement could be to log the Nvidia device names that the node is configured with on startup so it is clear to the user what devices are being used. Feel free to consider this for a separate PR though.

[jailuthra]

Fixed pending comments, and squashed+rebased on top of latest master. Also did some sanity testing on my 1060 again.

an additional UX improvement could be to log the Nvidia device names that the node is configured with on startup so it is clear to the user what devices are being used. Feel free to consider this for a separate PR though.

That would be a very cool feature. Will open a separate tracking issue for it.

[kyriediculous]

Requested changes look good to me, will let Yondon follow up on his change requests seperately.

[yondonfu]

LGTM

Windows build is failing due to what looks like a flaky gpg issue. Please trigger another build just to check if the Windows build passes and then this should be good to merge.

[jailuthra]

Squashed the fixup to trigger windows re-build. Everything works now. Merging.