Explore logging message levels within each Slic category

[kennyweiss]

Many logging tools have different logging levels to allow users to modify the verbosity at runtime.

Slic currently has:

• DEBUG
• INFO
• WARNING
• ERROR

Debug is automatically disabled during release builds. Info is the only non-warning level that's always available.

One possible solution would be to add levels to (each?) category, so users could ramp these up/down as desired at run time.

This will take some care to keep the interface intuitive.

Part of this could be resolved by https://github.com/LLNL/axom/issues/713

[rhornung67]

Maybe have levels for info and debug only?

[kennyweiss]

If we did this, we'd likely need to have a convention for how to assign the different levels, e.g. what differentiates a "level 2" message from a "level 3" message?

[kennyweiss]

This doesn't appear to be a high priority. Let's revisit if/when needed.