Improves zoom behavior in multi-plots

Refactors zoom handling in multi-plot scenarios to ensure consistent
axis ranges and proper synchronization between subplots, especially
when linking subplot axes.

Removes direct zoom event handling from subplots and centralizes zoom
logic in the multi-plot container.

This ensures that the 'Zoom All' operation correctly adjusts the
Y-axis ranges based on the configured aggregation method and linked
axes settings.

ApplicationLibCode/ProjectDataModel/Summary/RimSummaryMultiPlot.h

@@ -149,7 +149,6 @@ private:
     void appendCurveByStepping( int direction );
 
     void onSubPlotChanged( const caf::SignalEmitter* emitter );
-    void onSubPlotZoomed( const caf::SignalEmitter* emitter );
     void onSubPlotAxisChanged( const caf::SignalEmitter* emitter, RimSummaryPlot* summaryPlot );
     void onSubPlotAxisReloadRequired( const caf::SignalEmitter* emitter, RimSummaryPlot* summaryPlot );
     void onSubPlotAutoTitleChanged( const caf::SignalEmitter* emitter, bool isEnabled );