Add Alertmanager cases and transposer

[mvxt]

Summary

• If there are no alerts in the array of alerts from Alertmanager:
  • Summary will say "Alert from {receiver name}" instead of just "{receiver name}"
  • Description/Body will say "{receiver name} sent a webhook without any alerts or other information"
• If there is only one alert in the array:
  • Summary of FireHydrant alert will be the summary of the one alert (unchanged from CEL transposer)
  • Body of FireHydrant alert will be "{alert summary}: {alert description}\n"
• If there are multiple alerts in the array:
  • Summary will be "{number} alerts from {receiver name}"
  • Body of FireHydrant alert will be "{alert summary}: {alert description}\n" for every alert in array

Rather than summarizing multiple alerts only by the first alert's title and description (current behavior), we are including all alert summaries and bodies. The intention is to provide more clarity for multi-alert scenarios.

Annotations, links, and other param behaviors remain unchanged from CEL transposer.