multiregion: setup DRTs

[otan]

This issue is for coordinating work required to get somewhere closer to automatic DRTs.

In particular, our MVP here is to setup a way of making a DRT for multi-region work using TPC-C.

Steps:

• Setup --client-partitions to correctly send local traffic to all the tables. As of workload/tpcc: add multiregion TPC-C setup #65600, the new TPC-C workload is initialised on all cockroach machines, but the workload inserts data into other nodes resulting in un-optimised results. We should ensure the ./cockroach workload talks to the local region in the same node.
• Instrument workload to export prometheus metrics NOTE: unclear whether we should be using metrics.PrometheusExporter instead, but that's heavily tied to pkg/server/status which has a bunch of cruft we do NOT need
• Update the Chaos tooling to also log metrics and check that metrics perform as expect.

Epic CRDB-2541