Support for NVIDIA Jetson platforms

[jaywonchung]

NVML is not supported on Jetson platforms, e.g. Jetson Nano. Supporting Jetson platforms can be very useful for people who do ML/MLSys research on embedded platforms. Related discussion entry: #102

We can make this a new zeus.device.

Things to figure out:

• Get access to an actual Jetson device
• Try out the sysfs interface for power measurement (ref).
  • Is this for GPU only? Or is this CPU + GPU? Or the whole device?
  • What is the granularity of information exposed? How often does it update? Are there any overhead related to reading this?
• What about the energy consumption of DRAM, which is shared by the CPU and GPU?
• Are there any control knobs on the platform, like power limit?

[jaywonchung]

Ref: https://github.com/alumet-dev/alumet