feat(evals): add status enum for evaluation scores

[ssbushi]

Fixes #2252

Checklist (if applicable):

• PR title is following https://www.conventionalcommits.org/en/v1.0.0/
• Tested (manually, unit tested, etc.)
• Docs updated (updated docs or a docs bug required)

[ssbushi]

@pavelgj I made this override method to use the score and get a new status. should we make this even more generic and just pass in the full datapoint?

This is part of the plugin API so should be easy to fix.... I think?

[pavelgj]

does this fn need to know the metric? and maybe original status as well? so that one could do something like:

statusOverrideFn = ({score, originalStatus, metric}) => {
  if (metric === 'faithfulness') {
    return ...;
  }
  return originalStatus;
}

[ssbushi]

• originalStatus is available in the score object
• Since this is configured per metric, I think the metric field is redundant.

I like the idea of using an object for future expansion, so I added that.