feat(image): add `--docker-host` option for GH Action users

[calinmarina]

This is addressing problem arising from trying to scan local images when docker socket path is different than default /var/run/docker.sock

This was already requested and solved here https://github.com/aquasecurity/trivy/issues/2997 for CLI runs but not available for trivy GH Action.

Adds test and fixes outdated ones.

[CLAassistant]

All committers have signed the CLA.

[admiralAwkbar]

@uridium

Would you be able to get this merged back to master? Seems like an easy PR fix, and solves my issue in my current work as our docker-hosted runners mount on /run/docker/docker.sock

Thanks!

[uridium]

@admiralAwkbar it's not up to me, but @simar7