The status command was still trying to access ups.thresholds.battery which
no longer exists in v4.1+ configs. Thresholds are now in the actions array.
Changes:
- Updated displaySingleUpsStatus() to get thresholds from actions
- Finds first action with thresholds defined for battery symbol display
- Shows success/warning symbol only if threshold is defined
This fixes 'Cannot read properties of undefined (reading battery)' error
when running nupst status on v4.1+ configs.