Support showing Bandit issues by severity

[rahult-graphcore]

Bandit supports reporting on only high-severity issues using the -lll flag e.g.
bandit examples/*.py -n 3 -lll

or medium and high severity issues with -ll
bandit examples/*.py -n 3 -ll

This is quite useful when running on a large codebase to filter down to only the most serious issues.
This is a request to add this config option to Bandit in the Ruff linter.

[MichaReiser]

Hi

I can see how this is useful. We're considering to introduce a warning level to distinguish between different severities. See #1256

I don't think we want to go as far as having more levels other than warning and error. I'll close this in favor of #1256