Function parse_state 

pub async fn parse_state(
    stats: &mut SystemdUnitStats,
    unit: &ListedUnit,
    config: &UnitsConfig,
    connection: Option<&Connection>,
) -> Result<bool, MonitordUnitsError>

Parse state of a unit into our unit_states hash.

Returns true when an actual time-in-state D-Bus fetch was performed, so callers can keep state_dbus_fetches honest. Allowlist/blocklist short-circuits and state_stats_time_in_state = false both return false.