Display relay grace periods in both units

Relay grace-period settings currently show only one unit, obscuring the configured duration. Reimplement the two-unit formatter with settings coverage. Source PR https://github.com/stablyai/orca/pull/13838; credit @huhuhulululu. No contributor action requested.

Start with source PR #13838, which contains the implementation context for the two-unit relay grace-period formatter and its settings coverage. Confirm whether the issue is already resolved there; done means the configured grace period displays both units and the relevant settings coverage passes.

Written by the indexing model from the issue text.