Add 200k cap for partition result

[BenjaminBuick]

As stated in our article on partitions, the maximum number of partitions per broker is 4k, or 200k per cluster.

Of course, we do not advise pushing the number of partitions to these limits. But any result above 200k is only a theoretical number and has no practical relevance.

We should therefore set the upper limit for the partition result to 200k.

[nfma]

@BenjaminBuick I think you have a typo. it's 40k per broker, not 4k.