And some other changes, enough that I'm calling this v0.6.

- Make compression of traces configurable by the FUNCTIONTRACE_COMPRESSION env var
- Cleanup integration test formatting and disable trace compression
- Remove --max-threads argument to functiontrace-server (I didn't understand its purpose originally)
- Bump various dependency versions
- Upgrade the minimum version for CI to 3.7 since 3.6 is extremely EoLed