Better logging for Environments where the environment variable is not controlled

[berendsliedrecht]

Right now, env_logger is used just like in aries-askar and indy-vdr, but this can get rather annoying in React Native environments. The custom logger callback is causing some issues in Node.JS with regards to GC.

My proposed solution would be the following:

1. create set_logger(level: "debug" | "info" | "trace" | "env")

• This would just print the logs to stdout or stderr
• env would just do it like the current setup with RUST_LOG. This would still allow some nice flexibility with namespace logging.