Surprising default configuration for advisories

[djc]

Describe the bug

I was surprised to note that RUSTSEC-2022-0049 (which I happen to be aware of as a chrono maintainer) only generated a warning. After looking at the documentation I noticed that unsound defaults to warn, which I find quite surprising. Similarly, I think something stricter would be a better default for yanked.

In particular, this feedback pertains to running EmbarkStudios/cargo-deny-action@v1 in CI, where I'm pretty unlikely to notice the warnings -- and I think both of these should be noticeable by default when run in CI.

[Jake-Shadle]

The defaults were chose as warn basically because:

1. unsound advisories are informational and distinct from vulnerabilities, with a lower priority and thus a lower level.
2. People already complain about new advisories breaking their CI, yanking is in a similar vein, breaking your CI with no meaningful changes in the project.

These could be of course changed it would just be a breaking change that would require a new version of the action as well.