Reimplemented the Jetson class + miscellaneous additional changes

The existing Jetson does not work for AGX Xavier/Orin with Ubuntu 20.04 (Jetpack 5.0.2 GA). In this MR, the code is reimplemented with the help of a new Tegrastats class. This class reads the output of the tegrastats daemon to get the power measurements.

Some additional (API breaking) changes are also made in the process of testing the new Jetson class.