Switch from log to tracing crate for per-crate log levels

[detjensrobert]

Right now our verbosity flag sets a global log level. Some of our dependencies (bollard, kube) are very verbose at debug and trace levels, and setting our log level to debug for our debug logs should not enable their debug logs.

The log crate does not support this, and only has a global log level. The newer tracing crate (https://lib.rs/crates/tracing) which seems to be the new preferred logging crate can do separate global- and crate-specific log levels. It should be a drop-in replacement, and we can enable the other stuff it does after we switch.