logging: drop default OCI runtime log level from Into to Warn

[grahamwhaley]

Which feature do you think can be improved?

OCI kata runtime logs at a default level of Info, which is quite noisy in the logs.
When used as the containerd shimv2 runtime, the default (inherited from containerd itself) is Warn, which is much quieter, but still tells you of warnings and errors.

How can it be improved?

Let's drop the OCI runtime log level down to Warn, to save our end users log space and bandwidth - I really doubt anybody reads the Info logs....

Additional Information

We should consider if this will harm our, or our user, debug flow.
We probably want to cast a net to known active users to see if this might affect their current setup at all.

And as a side note, presently there is no way to enable anything else other than Debug level - so presently you can only go from Info->Debug, and can not afaik set a Warn level. With this change you will only be able to go from Warn->Debug level, with no mechanism to set an Info level. Adding the ability to choose nay default level would be a different Issue/PR I think.

[grahamwhaley]

I should note, we use logrus, and it has its levels documented here, with a hint that the default level is Info, and you can find that in the code here where it constructs the default logger I believe.