Describe the problem

We introduced a singleton AUTO SPAN CONFIG RECONCILATION job in #68522. We use this per-tenant job to drive the reconciliation process between a tenant's SQL config state (zone configs) with the cluster's KV state (span configs) -- more details found in the accompanying RFC. The RFC relies on strict mutual exclusion guarantees, needing to ensure that at a given point in time, only a single reconciliation instance is up and running. We're currently failing to provide this guarantee as described in the thread here: #71994 (review). This issue tracks fixing this bug.

Jira issue: CRDB-11751