roachtest,asim: validate asim

[kvoli]

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This patch adds a roachtest to validate the accuracy of the allocation simulator. It collects results of running identical configurations in simulated and real cluster.

The collected results are then compared, looking at the similarity of distributions for per-store metrics:

• lease count
• replica count
• queries per second
• write keys
• read keys
• write bytes
• read bytes

And comparing cluster metrics:

• range rebalance count
• lease transfer count
• rebalancing snapshot bytes

The roachtest will fail, without blocking the release if any of these measurements are different, beyond an error threshold.

Release note: None

[cockroach-teamcity]

This change is