[Ktrace] Spawn and synchronize the ktrace and benchmark processes

[JiriPavela]

The compiled userspace ktrace and benchmark processes are currently being invoked and terminated manually. Ktrace must automate correct spawning, synchronization and termination of those processes. However, ktrace and sometimes the benchmarks have to run with elevated privileges (sudo) which complicates things with subprocess. Ktrace needs to spawn a new python script with sudo privileges so that subprocess polling and termination of sudo processes works correctly.

• Create a separate collection script that will be invoked with sudo privileges and manage both ktrace and benchmark process.
• Correctly synchronize the two processes, most notably:
  • The benchmark process must start only after ktrace successfully loads and attaches the BPF program.
  • The ktrace process must be terminated only after the benchmark finishes (or a timeout is reached) and the leftover event records in the BPF ring buffer are processed.