KIP-685 — Loosen permission for listing reassignments

Discussion SecurityAdmin

Lowers the required permission to call `ListPartitionReassignments` from `ClusterDescribe` to `Topic:Describe` so that end users can distinguish under-replicated partitions caused by ongoing reassignments from those caused by broker failures. After KIP-339 required `ClusterDescribe` for this API, ordinary users lost the ability to differentiate reassignment-related URPs from failure-related URPs, regressing the observability improvement from KIP-352.

Details