Draft: Service Desk SLA timers [POC]

What does this MR do and why?

This is a POC for SLA timers for Service Desk.

Contributes to SLA Exploration (#462800)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Only timer for first response

Timer for first response and state badges (new and open)

Open state doesn't have a time-to-next-response timer yet.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.