Add Nsight SQLite reader

[lithomas1]

TODO:

• Formalize method for handling multiple "traces" in pipit
  • Nsight Systems contains many traces, interesting ones are
    • NVTX events
    • CUDA API trace (all cuda functions called)
    • Memory operations/Kernel Launches
• CPU/GPU Metrics
  • Some particularly interesting ones of note:
    • CPU Utilization/GPU utilization/Unified memory page faults, etc.
• Device Metadata
  • e.g. Might be interesting to attach metadata, such as GPU Name, GPU VRAM, # of SMs, etc. to the pipit Trace object (not on dataframe since not all dataframes can handle metadata)
  • Then we might be able to analyze perf across different types of GPUs (e.g. to figure out which GPU is right for which workload).
• Multi-device?
• Tests

cc @jhdavis8 since you were interested in the Nsight reader too

also cc @ocnkr since this is based off your previous PR.