Previously lorry-controller was not respecting the log-level setting specified
in the controller.conf file and setting it would not change the logging
behavior of the program. It was possible however to change the logging level
by setting the environment variable LORRY_LOG. This change removes the
use of the EnvFilter[1] filter and changes the logger to use the LevelFilter[2]
filter.

Setting `log-level = "debug"` in your controller.conf file or adding the flag
lorry-controller --log-level=debug will now configure the logger as expected.

When both a CLI flag and configuration file option are present the CLI flag
will take precedence.

Log messages have additionally been improved for both the controller and worker.

A new helper function named redact has been added to the utils module to
remove sensitive strings from log messages.

1.https://docs.rs/tracing-subscriber/0.2.19/tracing_subscriber/filter/struct.EnvFilter.html
2.https://docs.rs/tracing-subscriber/0.2.19/tracing_subscriber/filter/struct.LevelFilter.html