Investigate about grouping metrics by status code

[SantiagoPittella]

One thought for querying metrics is that maybe we want to group all responses under a single metric with a "status code" label. Then queries become more versatile (status_code >= 400, etc.). But maybe this is overkill for now because the amount of different responses is narrow enough that it can be handled separately (and maybe this was discussed already).

Originally posted by @igamigo in 0xMiden/protocol#1017 (comment)