Unify the width of all visible legends.

* Calculate the minimum width to fit the content before the render pass.
  * Set the actual width of all the legends to the largest of the minimum widths.
  * This resizes the legends to always be the same size and reduces the size of you remove
     the widest legend.

ApplicationCode/ProjectDataModel/RimLegendConfig.cpp

@@ -370,6 +370,7 @@ void RimLegendConfig::updateLegend()
        numDecimalDigits -= static_cast<int>(decadesInRange);
    }
    m_scalarMapperLegend->setTickPrecision(cvf::Math::clamp(numDecimalDigits, 0, 20));
+   m_scalarMapperLegend->computeLayoutAndExtents();
 
    RiaApplication* app = RiaApplication::instance();
    RiaPreferences* preferences = app->preferences();