[Ktrace] Implement event parsing directly in the userspace C program

[JiriPavela]

Event records in Ktrace are being stored in a temporary data file and later parsed in Python. This is rather slow and processing the events directly in the userspace ktrace C program should be much faster. However, we might need larger BPF ring buffer to offset the slower event processing compared to simply storing the events in a file.

This could apply to other profilers (tracer+eBPF, tracer+PIN)