[tempo-distributed] Enable autoscaling for Compactor

[7onn]

I was oncall and this alert introduced me to this runbook.

Even though I manually scaled out the workload and fixed the issue, I couldn't help but to think that it would make sense to automate this behavior based on the metric that triggered it.

Therefore, I'd like you folks to assess the feasibility of having an autoscaling feature like the one introduced here: #2817