Use settings keys, not error codes, for ERC/DRC reports

Error codes can shift around if the enum ordering is
not maintained, which is more fragile than the settings
key which should never be changed after a new code is
created.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/6001

common/rc_item.cpp

@@ -87,8 +87,8 @@ wxString RC_ITEM::ShowReport( EDA_UNITS aUnits, SEVERITY aSeverity,
 
     if( mainItem && auxItem )
     {
-        return wxString::Format( wxT( "ErrType(%d): %s %s\n    %s: %s\n    %s: %s\n" ),
-                                 GetErrorCode(),
+        return wxString::Format( wxT( "[%s]: %s %s\n    %s: %s\n    %s: %s\n" ),
+                                 GetSettingsKey(),
                                  GetErrorMessage(),
                                  severity,
                                  ShowCoord( aUnits, mainItem->GetPosition() ),
@@ -98,8 +98,8 @@ wxString RC_ITEM::ShowReport( EDA_UNITS aUnits, SEVERITY aSeverity,
     }
     else if( mainItem )
     {
-        return wxString::Format( wxT( "ErrType(%d): %s %s\n    %s: %s\n" ),
-                                 GetErrorCode(),
+        return wxString::Format( wxT( "[%s]: %s %s\n    %s: %s\n" ),
+                                 GetSettingsKey(),
                                  GetErrorMessage(),
                                  severity,
                                  ShowCoord( aUnits, mainItem->GetPosition() ),
@@ -107,8 +107,8 @@ wxString RC_ITEM::ShowReport( EDA_UNITS aUnits, SEVERITY aSeverity,
     }
     else
     {
-        return wxString::Format( wxT( "ErrType(%d): %s %s\n" ),
-                                 GetErrorCode(),
+        return wxString::Format( wxT( "[%s]: %s %s\n" ),
+                                 GetSettingsKey(),
                                  GetErrorMessage(),
                                  severity );
     }

eeschema/erc_item.cpp

@@ -36,6 +36,8 @@
 #undef _
 #define _(s) s
 
+// NOTE: Avoid changing the settings key for an ERC item after it has been created
+
 ERC_ITEM ERC_ITEM::duplicateSheetName( ERCE_DUPLICATE_SHEET_NAME,
         _( "Duplicate sheet names within a given sheet" ),
         wxT( "duplicate_sheet_names" ) );

pcbnew/drc/drc_item.cpp

@@ -36,6 +36,8 @@
 #undef _
 #define _(s) s
 
+// NOTE: Avoid changing the settings key for a DRC item after it has been created
+
 DRC_ITEM DRC_ITEM::unconnectedItems( DRCE_UNCONNECTED_ITEMS,
         _( "Unconnected items" ),
         wxT( "unconnected_items" ) );