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Description
Part of #136667
There are around 31 usages of roachpb.MustMakeTenantID(2) in tests used for application tenant. We should be replacing them with tenant id 3 and disallow creating secondary tenants with id 2. This would align with real world scenario where tenant with id 2 doesn't exist, which is enforced in demo cluster and normal operations. And if a cluster goes through UA migration, tenant 2 would be a system tenant.
Jira issue: CRDB-46349