ADDED: Cross-probe highlighting of bus members

Note: this is a basic implementation but it could be
improved once we include bus information in the netlist
and pcbnew can natively keep track of buses and nets
instead of just nets.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/4158

common/render_settings.cpp

@@ -27,6 +27,7 @@ using namespace KIGFX;
 
 
 RENDER_SETTINGS::RENDER_SETTINGS() :
+        m_highlightNetcodes(),
         m_printDC( nullptr )
 {
     // Set the default initial values
@@ -36,7 +37,6 @@ RENDER_SETTINGS::RENDER_SETTINGS() :
     m_highlightEnabled   = false;
     m_hiContrastEnabled  = false;
     m_hiContrastFactor   = 0.2f; //TODO: Make this user-configurable
-    m_highlightNetcode   = -1;
     m_outlineWidth       = 1;
     m_worksheetLineWidth = 100000;
     m_defaultPenWidth    = 0;