feat: logging: Enable per-module log level

One very handy feature of env_logger (which Foundations doesn't use afact) is that one can set log level on a per-module basis. I'd very much like this capability, because some crates we are using (e.g. Hyper) log a lot at DEBUG level, and this is noise when looking at the debug logs from our actual app.

Anyway, I've been poking around the code in telemetry/log/init.rs a little. Wanted to open an issue in case anyone else had this on their radar and was already looking at this, or else feel free to assign to me and I can take a stab at a PR. Thanks.