Is your feature request related to a problem? Please describe.

We need a set of library functions in the roachtest package, or to use when writing roachtests, to make authoring admission control integration tests + experiments (#89208) easier. For ex:

• summary metrics for the test run so we don't have to examine graphs: e.g. throughput, throughput variance, latency percentiles etc. for each workload. some existing/new (clusterstats for ex.) library components in the roachtest package may be developed, maybe emitting to roachperf/replacement. want to measure things like '% of time latency was over Xms' for a few values of X, or '% of time between T and T+t where throughput was below Y'. both things to evaluate latency and performance isolation of admission control.
  • bonus points if you can segment this by tenants in multi-tenant roachtests, or by workload in multi-workload experiments
• some helper struct in the roachtest package that envelopes manual cgroup mucking and for different things like CPU/disk bandwidth/IOPs
• some helper struct in the roachtest package to auto collect outlier traces that are now possible with stmtdiagnostics: support continuous bundle collection #83020 + stmtdiagnostics: support probabilistic bundle collection #82750. would be good to end a test with a set of outlier traces from that test run
• library functions in roachtest to attach VMs to disk images pre-loaded with previous CRDB cluster state. better way to run experiments with full-ish LSMs that take time to fill up (possibly useful in db: benchmark framework for compaction heuristic comparisons pebble#1865). should have a parallel where roachtests actually generate disk images to use for future experiments. has to be captured over a CRDB cluster that's wound down entirely to get a consistent disk snapshot
• roachprod,roachtest: support tenants #78484

Jira issue: CRDB-20528