refactor(modules): use ALabel dedup tooltip helper in simpleclock, systemd-failed-units, upower

simpleclock: migrate to updateLabelAndTooltip (label + tooltip share the
localtime arg; default tooltip falls back to the label format).
systemd-failed-units: use setLabelMarkup/setTooltipMarkup dedup setters;
label/tooltip formats are selected by different conditions so the combined
helper does not apply.
upower: use setLabelMarkup for the label; tooltip stays a custom GTK widget.
mpd already uses the dedup setters (label/tooltip use different truncated
args), so no change.

src/modules/upower.cpp

@@ -223,7 +223,7 @@ auto UPower::update() -> void {
     return;
   }
 
-  label_.set_markup(getText(upDevice_, format_));
+  setLabelMarkup(getText(upDevice_, format_));
   // Set icon
   if (upDevice_.icon_name == NULL || !gtkTheme_->has_icon(upDevice_.icon_name))
     upDevice_.icon_name = (char*)NO_BATTERY.c_str();