How do we still expose to the user that a diagnostic was a warning with `warn-as-error`

Moving option 3 discussion into a new issue from #2972

When using `--warn-as-error` all warnings are converted to error(which makes sense from the name) However this means that users only see errors when enabled(common in CI). This result in people not knowing if those are actually just warning that can be suppress or actual errors that should get resolved

One options would be to still display them as warning in the CLI by keeping a `originalSeveirty` entry on the diagnostic saved on the program.
Another option would be to have a different flag to keep warning but still make it fail `--fail-on-warning`