Enhance observability into Admission Control based resource usage.

**Is your feature request related to a problem? Please describe.**
When using metrics in CRDB to alert, it would be nice to see the CPU utilization for just the workload excluding what is in use by Admission Control. This graph is alarming to the customer as it shows 95% CPU utilization (or more) and removes the ability to alert on CPU usage over 75% which is where we generally advise that they increase their cluster size.

**Describe the solution you'd like**
Two separate graphs. One for TOTAL CPU utilization and one for foreground CPU utilization

**Describe alternatives you've considered**
Cap Admission Control utilization at a value between 65 and 75%

**Additional context**

Jira issue: CRDB-28133