API: Preserve linked symbol properties in footprints

Fixes https://gitlab.com/kicad/code/kicad/-/issues/21655


(cherry picked from commit 949be9a63a)

Co-authored-by: Jon Evans <[email protected]>

common/api/api_utils.cpp

@@ -242,4 +242,14 @@ KICOMMON_API void PackSheetPath( types::SheetPath& aOutput, const KIID_PATH& aIn
         aOutput.add_path()->set_value( entry.AsStdString() );
 }
 
+KICOMMON_API KIID_PATH UnpackSheetPath( const types::SheetPath& aInput )
+{
+    KIID_PATH output;
+
+    for( const types::KIID& sheet : aInput.path() )
+        output.push_back( KIID( sheet.value() ) );
+
+    return output;
+}
+
 } // namespace kiapi::common