Make `NopLogger` public

[tommasoclini]

I think it would be nice to have a ready to use nop logger from the application side.

[Thomasdezeeuw]

The NopLogger is the same as not setting a logger, why would it need to be set?

[tommasoclini]

In some cases it can be helpful, for example when not using the default logger, but you want to turn off logging for a specific struct.

[Thomasdezeeuw]

How would that work? NopLogger doesn't do anything, it doesn't any thing for a "specific struct".

[tommasoclini]

I'll tell you my specific use case, I'm trying to add a logger to the ergot stack, instead of using the default one, and the logger would be a field of a struct.
By default, the logger would be a &NopLogger, then the user can set a logger with a function set_logger.
It would be nice to have a ready to use NopLogger instead of copying and pasting it.

[Thomasdezeeuw]

@KodrAus what do you think? I'm not quite convinced that not having to copy 10 lines of code, that basically do nothing, is enough of an argument to maintain the additional API.