Making some small changes that would hopefully improve performance a bit.
- Remove redundant string generations for CPU data conversion
- Switch to fnv for PID hashmap and hashsets
- Use buffered reading to avoid having to store too many lines as strings
Fixes some performance regressions and forgotten cleanup.
Changes to attempt to improve performance to match 0.4.x:
- Remove `trace!` and `--debug` for now. These were a significant hog. Removing this dropped initial memory usage by about half.
- Add additional cleaning step for `pid_mapping` during process harvesting. This should hopefully improve memory usage as time goes on.
- Slightly change how we do sorting to hopefully be a bit more optimal? This was just an easy change to make that I spotted.
- Fix broken cleaning child thread task.
