refactor: the Sonar remarks on the small fixes taken care of

- the log stops through a flag kept in a function, not a global one
- the messages are put together with std::format
- a vehicle dropped on a trainset in the launcher goes in once the
  trainset is drawn, so the vehicles are gone through with a plain loop
  again; the drop split into a new vehicle and a moved one
- the scenario that can't be opened is caught as the runtime error it
  is, a file name outside of the code page as the system error it is
- a track of an unknown type is left out through the pointer owning it
- the keyword of a track type written out by a function of its own
- the picked node forgotten with ranges::replace_if, the empty
  Forget_Node of the base renderer told why it is empty
- FileCased takes the path it works on

simulation/simulationstateserializer.cpp

@@ -36,6 +36,7 @@ http://mozilla.org/MPL/2.0/.
 #include "utilities/utilities.h"
 #include "editor/editorTerrainStreamer.hpp"
 
+#include <format>
 
 namespace simulation {
 
@@ -542,13 +543,14 @@ state_serializer::deserialize_node( cParser &Input, scene::scratch_data &Scratch
     }
     else if( nodedata.type == "track" ) {
 
-        auto *path { deserialize_path( Input, Scratchpad, nodedata ) };
-        if( path->eType == tt_Unknown ) {
-            // with no path made it can't be joined nor drawn, and nothing could run on it
-            ErrorLog( "Bad scenario: track \"" + path->name() + "\" of an unknown type defined in file \"" + Input.Name() + "\" (line " + std::to_string( inputline ) + ") left out" );
-            delete path;
+        std::unique_ptr<TTrack> made { deserialize_path( Input, Scratchpad, nodedata ) };
+        if( made->eType == tt_Unknown ) {
+            // with no path made it can't be joined nor drawn, and nothing could run on it: it goes with its holder
+            ErrorLog( std::format( "Bad scenario: track \"{}\" of an unknown type defined in file \"{}\" (line {}) left out", made->name(), Input.Name(), inputline ) );
             return;
         }
+        // from here on the scene owns it
+        auto *path { made.release() };
         // duplicates of named tracks are currently experimentally allowed
         if( false == simulation::Paths.insert( path ) ) {
             ErrorLog( "Bad scenario: duplicate track name \"" + path->name() + "\" defined in file \"" + Input.Name() + "\" (line " + std::to_string( inputline ) + ")" );