docs(packetparser): add concise buffer-selection decision guidance

[agrawaliti]

Summary

• update packetparser performance section with a balanced, benchmark-backed comparison of perf_event_array and ringbuf
• add concise customer decision guidance for buffer selection based on traffic rate, topology, and CPU/sample-drop budget
• add a minimal validation flow to compare both modes on the same node pool

Notes

• keeps recommendations practical and workload-specific (no universal claims)
• includes ring buffer sizing guidance for high sustained packet rates