asim: enable faster dev feedback and expand test coverage

[kvoli]

Overview This is a tracking issue for a series of features to be added into the allocation simulator asim.

This follows from the previous tracking issue (https://github.com/cockroachdb/cockroach/issues/82627), which entailed creating an MVP of the allocation simulator.

The current stock of features supported:

• cluster rebalancing
  • replicate queue (lease, replica count)
  • store rebalancer (QPS)
• load based and size based splitting.
• the KV workload for point read/writes
• gossip with a fixed delay propagation
• metrics for per-store state and actions

Objectives

(1) Increase development speed by making the simulator easily harnessed and reliable for testing patches. (2) Expand test coverage of the allocation system.

Issues

• [x] https://github.com/cockroachdb/cockroach/issues/90138
• [ ] https://github.com/cockroachdb/cockroach/issues/90139
• [x] https://github.com/cockroachdb/cockroach/issues/90141
  • [x] https://github.com/cockroachdb/cockroach/issues/90533

Jira issue: CRDB-20607

[kvoli]

dropped from 23.1 due to staffing. Moving #90140 which is still planned, to tracking issue #90582.