fix(cli): always output fatal errors to stderr

[knqyf263]

Description

--quiet currently suppresses even fatal errors.

Before

$ trivy image unknown --quiet 

After

$ trivy image unknown --quiet
2024-05-30T16:16:14+04:00        FATAL   Fatal error     image scan error: scan error: unable to initialize a scanner: unable to initialize an image scanner: unable to find the specified image "unknown" in ["docker" "containerd" "podman" "remote"]: 4 errors occurred:
        * docker error: unable to inspect the image (unknown): Error response from daemon: No such image: unknown:latest
        * containerd error: containerd socket not found: /run/containerd/containerd.sock
        * podman error: unable to initialize Podman client: no podman socket found: stat podman/podman.sock: no such file or directory
        * remote error: GET https://index.docker.io/v2/library/unknown/manifests/latest: UNAUTHORIZED: authentication required; [map[Action:pull Class: Name:library/unknown Type:repository]]

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).

[chen-keinan]

Thanks!!

[chen-keinan]

@knqyf263 lgtm 🚀