Provide idiomatic abstraction for vGPU type information

[christoph-heiss]

Pretty straight forward overall. Introduces a new VgpuType struct, which wraps over a nvmlVgpuTypeId_t and a proper idiomatic way to access these informations.

I'v also added a Nvml::lib() method, for accessing the underlying (raw) library from the abstraction. This would be useful for e.g. calling functions which are not yet abstracted in nvml-wrapper, without having to completely use nvml-wrapper-sys and NIH, basically. Hopefully that is acceptable.

[christoph-heiss]

Ping. Is this of any interest for this library?

[thinkingfish]

@christoph-heiss Thanks for the ping. A bit of background is that we (IOP Systems) became the primary maintainer of this repo earlier this year, after the original owner took a job that made it tricky for them to contribute to OSS. This PR was submitted before we came on board, and fell through the crack a bit during this transition. We will take a look and hopefully get it merged soon.

[christoph-heiss]

Thanks for the review! I've fixed both nits.

[swlynch99]

I'm gonna go ahead and merge this as it's been a few months and the code LGTM. Thanks for the PR!