asim: validate unified rebalancing

[kvoli]

The simulator will simulate load based rebalancing and range count. The usefulness of the simulation is dependent on how accurately it reflects an actual cockroach cluster performing the same task.

Validate the simulated replica movements, lease transfers and load based splits that occur as a result of rebalancing where both the simulated and real cluster have identical settings, outlined in #83989.

additional

It may also prove useful to separate load based rebalancing into it's own validation, as is done for range count rebalancing. This issue specifies both be tested at the same time, as would occur under default settings in a production cluster.

Jira issue: CRDB-17391