log level in cli

[RCasatta]

After the introduction of the --log_level cli parameter, we lost the ability to filter logs by package making it unusable for log levels like debug or more granular (because there is too much output from package like rustls and sled).

example

RUST_LOG=debug,sled=info,rustls=info cargo run ...

I think we should either:

• remove --log_level parameter
• if possible accept in --log_level the same format supported in RUST_LOG and even allow RUST_LOG to work in alternative (I missed the --log_levelupdate and I started trying to use RUST_LOG automatically which is the standard in the rust ecosystem and I was surprised it had no effect)

[eupn]

I think it makes sense to only use RUST_LOG for anything logging-related. It's an industry standard and a lot of rustaceans expect this env var to work out of the box.